Raspberry Pi Email Server Part 2: Dovecot

Dovecot Logo

This is the second part of a five part tutorial that will show you how to install a full featured email server on your Raspberry Pi. This tutorial covers Dovecot, which provides SASL authentication and IMAP capabilities. The parts are:

The Introduction & Contents Page (read first)
Raspberry Pi Email Server Part 1: Postfix
Raspberry Pi Email Server Part 2: Dovecot
Raspberry Pi Email Server Part 3: Squirrelmail
Raspberry Pi Email Server Part 4: Spam Detection with Spamassassin
Raspberry Pi Email Server Part 5: Spam Sorting with LMTP & Sieve

Fixing the errors that appeared during dovecot installation

In part 1, when you installed Dovecot I mentioned that you might see some errors like this:

Creating config file /etc/dovecot/conf.d/20-imap.conf with new version
[....] Restarting IMAP/POP3 mail server: dovecotError: socket() failed: Address family not supported by protocol
Error: service(imap-login): listen(::, 143) failed: Address family not supported by protocol
Error: socket() failed: Address family not supported by protocol
Error: service(imap-login): listen(::, 993) failed: Address family not supported by protocol
Fatal: Failed to start listeners
 failed!
invoke-rc.d: initscript dovecot, action "restart" failed.
dpkg: error processing dovecot-imapd (--configure):
 subprocess installed post-installation script returned error exit status 1
Setting up dovecot-ldap (1:2.1.7-7) ...

These errors are caused by the lack of IPv6 support, which I mentioned in the previous tutorial. To remove the errors, open the main dovecot configuration file (/etc/dovecot/dovecot.conf) and find this line:

listen = *, ::

And change it to:

listen = *

The * means “all IPv4 addresses”, the :: means “all IPv6 addresses”. Now restart Dovecot, and you shouldn’t get any errors:

sudo service dovecot restart

Note: since I wrote this tutorial, there have been a few small changes to the default configuration file - you may find that the line is commented (with a # at the start of the line). If so, remember to uncomment it when you make your changes!

Tell Dovecot where your Mailbox is

Open /etc/dovecot/conf.d/10-mail.conf and find this line:

mail_location = mbox:~/mail:INBOX=/var/mail/%u

Change it to this:

mail_location = maildir:~/Maildir

Instruct Postfix to use Dovecot SASL

Now we need to tell Postfix that we would like to use Dovecot for SASL authentication. Open /etc/postfix/main.cf and add these lines:

smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes

Now tell Dovecot to listen for SASL authentication requests from Postfix. Open /etc/dovecot/conf.d/10-master.conf and comment out the current block that begins with service auth (place a # at the start of each line). Replace it with this:

service auth {
        unix_listener /var/spool/postfix/private/auth {
                mode = 0660
                user = postfix
                group = postfix
        }
}

Now you want to enable plain text logins. Do it by adding these two lines to /etc/dovecot/conf.d/10-auth.conf. Make sure they are not already present in the file, or your settings may be overwritten with the default ones if the default is declared later in the file than the lines you add. If the parameters are already present, you can either modify the existing lines or comment them out and add these new ones:

disable_plaintext_auth = no
auth_mechanisms = plain login

Note that although the logins are in plain text, we will be setting Postfix up later so that it only allows you to use plaintext logins from within SSL/TLS. This means that your login and password will sent in an encrypted session - you wouldn't see them in plain text if you used a packet sniffer, for example. For now, we’re allowing unencrypted plain text logins so that we can test logging in with Telnet. Since the connection is local (from the Pi to the Pi), your password isn’t being sent over any insecure networks so this is fine.

Testing SASL

Creating a new user for testing purposes is a good idea. Let’s call this temporary user testmail and give it the password test1234 Use this command to add the user, and follow the prompts including setting a password.

sudo adduser testmail

Now restart Postfix and Dovecot:

sudo service postfix restart
sudo service dovecot restart

We’re now going to try and send an email after authenticating with SASL. The server is expecting to see a base64 encoded version of your username and password, so we have to convert it first. There are three ways of doing this, so I've given examples below using the testmail username and test1234 password:

#Method No.1
echo -ne '\000testmail\000test1234' | openssl base64

#Method No.2
perl -MMIME::Base64 -e 'print encode_base64("\0testmail\0test1234");'

#Method No.3
printf '\0%s\0%s' 'testmail' 'test1234' | openssl base64

I have discovered that if your password starts with a number, methods 1 and 2 don’t work. Assuming the username and password are testmail and test1234, the commands produce this:

AHRlc3RtYWlsAHRlc3QxMjM0

WARNING: If you’re having problems with authentication and you paste examples to forums or mailing lists, be aware that it is really easy to convert this back into your username and password (hence the creation of a test user). If you're using your real username and password to test, redact it before posting!

Now, still logged into the Pi via SSH, you can telnet port 25 to test whether or not SASL is working. There’s only one extra step, which is the AUTH PLAIN command that comes after ehlo but before mail from. For testing, the permit_mynetworks parameter should be commented out under your postfix smtpd_recipient_restrictions block in /etc/postfix/main.cf. If you’re following on from Raspberry Pi Email Server Part 1: Postfix then this should already be the case. If you have to change it, remember to reload postfix (sudo service postfix reload) after you change the value. Here’s an example:

telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 samhobbs ESMTP Postfix (Debian/GNU)
ehlo facebook.com
250-samhobbs
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
AUTH PLAIN AHRlc3RtYWlsAHRlc3QxMjM0
235 2.7.0 Authentication successful
mail from:testmail
250 2.1.0 Ok
rcpt to:me@externalemail.com
250 2.1.5 Ok
data
354 End data with .
Subject: This is my first email that has been authenticated with Dovecot SASL
Woop woop
.
250 2.0.0 Ok: queued as B87133F768
quit
221 2.0.0 Bye
Connection closed by foreign host.

Now try again but enter the username/password incorrectly (base64 encode something random) – you should get an error message and the email won’t send. If everything went to plan, then SASL is working properly!

You can now uncomment permit_mynetworks again.

Separating Incoming email (unauthenticated) from Outgoing Email (SASL authenticated)

It’s probably a good idea to have a dedicated port for sending outgoing email…here’s why: Port 25 doesn’t require (but does offer) SSL/TLS encryption. If you mess up configuring your mail client you could end up letting it authenticate with SASL over insecure connections. Using a different port that only accepts SSL/TLS connections removes the risk that a poorly configured email client could be sending your password unencrypted over dodgy networks. There are two ports you can use for this:

  1. 465: SMTP over SSL
  2. 587: Email submission

587 is the “official” port for email clients (like K9 mail, Thunderbird and Outlook) to use when submitting messages to the Mail Submission Agent (your email server) – the submission may be encrypted or unencrypted depending on the server configuration. 465 was a port that was assigned for SMTP with SSL/TLS before the STARTTLS protocol was introduced, back in the days when you chose your port and that decided on the type of connection you were going to get (encrypted or unencrypted).

STARTTLS changed things because it allows you to connect with an unencrypted connection (like the one you get with Telnet), and then upgrade to an encrypted connection without changing port… so when STARTTLS was introduced, SMTPS on port 465 was removed from the standard because you could do the same thing with a single port (25).

However, I think there is some value in specifying a port for submission that only accepts SSL/TLS encrypted connections, and won’t work if the connection isn’t encrypted. This means that if you misconfigure your email client it just won’t work, instead of working and sending your password in an unencrypted format. So, anyway… Here’s how to set up Postfix to listen on port 465 for encrypted connections. The first step is telling Postfix to listen on port 465, so open /etc/postfix/master.cf and uncomment the line:

smtps     inet  n       -       -       -       -       smtpd

Now restart Postfix:

sudo service postfix restart

Test whether Postfix is listening on port 465:

telnet localhost 465
Trying 127.0.0.1...                                                                           
Connected to localhost.                                                                       
Escape character is '^]'.
220 samhobbs.co.uk ESMTP Postfix (Debian/GNU)
ehlo samhobbs.co.uk
250-samhobbs
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
quit
221 2.0.0 Bye
Connection closed by foreign host.

OK, so now it’s listening on the right port, but it’s allowing unencrypted connections. Here’s how you force TLS on port 465: open /etc/postfix/master.cf and find the line you uncommented earlier. Below it are some options, you want to edit them so that they look like this (i.e. uncomment lines 2 and 3):

smtps     inet  n       -       -       -       -       smtpd
  -o syslog_name=postfix/smtps
  -o smtpd_tls_wrappermode=yes

Line 3 is forcing TLS on port 465, and line 2 means that connections to port 465 have a different label in the logs, which can be useful for debugging.

sudo service postfix restart

Now try connecting with Telnet again… you should be able to establish a connection, but not receive any prompts from the server:

telnet localhost 465                                            
Trying 127.0.0.1...                                                                           
Connected to localhost.
Escape character is '^]'.
exit
exit
Connection closed by foreign host.

Now try openssl:

openssl s_client -connect localhost:465 -quiet
depth=0 CN = samhobbs
verify error:num=18:self signed certificate
verify return:1
depth=0 CN = samhobbs
verify return:1
220 samhobbs.co.uk ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye

Good: we are able to start a TLS encrypted connection. We got some errors because the certificate is self-signed (it's not signed by a certificate that is in the trusted root store on the server) but this is OK because we're just using the certificate for testing for now. When you come back later to set up a proper certificate, you can use this command to verify it. The -CApath option tells openssl where the trusted certificates are stored on your system:

openssl s_client -connect localhost:465 -quiet -CApath /etc/ssl/certs

Successful validation looks something like this:

sam@samhobbs:~$ openssl s_client -connect localhost:465 -quiet -CApath /etc/ssl/certs
depth=3 C = SE, O = AddTrust AB, OU = AddTrust External TTP Network, CN = AddTrust External CA Root
verify return:1                                                                              
depth=2 C = GB, ST = Greater Manchester, L = Salford, O = COMODO CA Limited, CN = COMODO RSA Certification Authority
verify return:1                                                                              
depth=1 C = GB, ST = Greater Manchester, L = Salford, O = COMODO CA Limited, CN = COMODO RSA Domain Validation Secure Server CA
verify return:1                                                                              
depth=0 OU = Domain Control Validated, OU = PositiveSSL, CN = samhobbs.co.uk                 
verify return:1                                                                              
220 samhobbs.co.uk ESMTP Postfix (Ubuntu)                                                    
quit                                                                                         
221 2.0.0 Bye

There are a couple more changes we want to make here: first, tell Postfix to only advertise SASL authentication over encrypted connections (so that you don’t accidentally send your password in the clear). Open /etc/postfix/main.cf and add this line:

smtpd_tls_auth_only = yes
sudo service postfix reload

Now connect to port 25 and you shouldn’t see AUTH advertised:

telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 samhobbs.co.uk ESMTP Postfix (Debian/GNU)
ehlo samhobbs.co.uk
250-samhobbs.co.uk
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

Lastly, we want to override the smtp_recipient_restrictions for port 465 so that it doesn't accept incoming messages from unauthenticated users.

At first, I didn't make this change and I noticed that some spam emails were coming in on port 465 and bypassing my spam filter, which I configured to scan all incoming email on port 25, but not 465 because I only expected it to be used for outgoing email. We can do this by overriding the smtp_recipient_restrictions list for port 465 in /etc/postfix/master.cf. Open master.cf and find the smtps line. Add a new recipient restrictions list option like this:

smtps     inet  n       -       -       -       -       smtpd
  -o syslog_name=postfix/smtps
  -o smtpd_tls_wrappermode=yes
  -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject

Now reload postfix:

sudo service postfix reload

Perfect! Postfix configuration is now complete.

Testing IMAP

There are two main protocols for fetching mail: POP and IMAP. The main difference between them is what they do with emails when they collect them: a POP client will fetch email from your server and remove it from the server when it’s done. This is inconvenient if you want to connect with two or more devices (like a phone and a computer) and have complete copies of all your emails on both. IMAP, on the other hand, makes a copy of the emails on the server and leaves the originals there. For this reason, I think IMAP is much more useful than POP and I didn’t even bother to set up POP on my server. We can now test the IMAP server with Telnet in a similar way to SMTP & SASL testing earlier. This time, we’ll be using port 143, the standard port for IMAP. The stages are:

  1. establish a connection with telnet localhost 143
  2. log in with a login "USERNAME" "PASSWORD"" (not base64 encoded this time)
  3. select inbox to see messages inside b select inbox
  4. logout with c logout

In case you're wondering, the "a b c" thing is done because a client can send multiple commands to the server at once, and they might not come back in the same order depending on what they are. So, the responses have the same letter as the commands they are responding to so that the client doesn't get muddled.

Here’s an example, using the testmail user we created earlier:

telnet localhost 143
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
a login "testmail" "test1234"
a OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE] Logged in
b select inbox
* FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
* OK [PERMANENTFLAGS (\Answered \Flagged \Deleted \Seen \Draft \*)] Flags permitted.
* 1 EXISTS
* 0 RECENT
* OK [UNSEEN 1] First unseen.
* OK [UIDVALIDITY 1385217480] UIDs valid
* OK [UIDNEXT 2] Predicted next UID
* OK [NOMODSEQ] No permanent modsequences
b OK [READ-WRITE] Select completed.
c logout
* BYE Logging out
c OK Logout completed.
Connection closed by foreign host.

Adding TLS support

Now that we know IMAP is working, we need to enable IMAPS (imap with SSL/TLS). The standard port for this is 993.

Many other tutorials that were written for older versions of dovecot will tell you to do this in different ways that won’t work, I tried 3 different methods before I ended up with a working one.

First, edit /etc/dovecot/conf.d/10-master.conf, find the “service imap-login” block and uncomment the port and SSL lines so that it looks like this:

service imap-login {
  inet_listener imap {
    port = 143
  } 
  inet_listener imaps {
    port = 993
    ssl = yes
  }
}

Edit 14/10/2015: the default dovecot configuration files changed recently after Jessie became the new stable distribution of Debian, which caused some users problems; TLS on port 993 used to be enabled by default but now it isn't. We need to re-enable it.

In /etc/dovecot/conf.d/10-ssl.conf, find ssl = no and change it to:

ssl = yes

There have been some security vulnerabilities discovered in older versions of the SSL protocol in recent times. SSLv2 is disabled by default, but it doesn't harm to explicitly disable it again. SSLv3 is vulnerable to an attack called POODLE, so we will disable it too. In the same file, find the ssl_protocols parameter line, uncomment it and add !SSLv3 to the end, like this:

ssl_protocols = !SSLv2 !SSLv3

Edit 02/09/2017: if you're using Debian Stretch or later, or one of its derivatives, then you will need to edit that line to match the following. The SSLv2 option is no longer recognised as an option for ssl_protocols because it has been removed entirely:

ssl_protocols = !SSLv3

For some bizarre reason, the Dovecot package for Raspberry Pi (and possibly newer versions of Ubuntu) does not create a self-signed certificate during installation like it used to. So, we have to create one manually. If you look in /usr/share/dovecot/ you will find the script that used to be used to generate the certificate; we can use it ourselves to simplify the process.

The script is located at /usr/share/dovecot/mkcert.sh and looks like this:

#!/bin/sh

# Generates a self-signed certificate.
# Edit dovecot-openssl.cnf before running this.

OPENSSL=${OPENSSL-openssl}
SSLDIR=${SSLDIR-/etc/ssl}
OPENSSLCONFIG=${OPENSSLCONFIG-dovecot-openssl.cnf}

CERTDIR=/etc/dovecot
KEYDIR=/etc/dovecot/private

CERTFILE=$CERTDIR/dovecot.pem
KEYFILE=$KEYDIR/dovecot.pem

if [ ! -d $CERTDIR ]; then
  echo "$SSLDIR/certs directory doesn't exist"
  exit 1
fi

if [ ! -d $KEYDIR ]; then
  echo "$SSLDIR/private directory doesn't exist"
  exit 1
fi

if [ -f $CERTFILE ]; then
  echo "$CERTFILE already exists, won't overwrite"
  exit 1
fi

if [ -f $KEYFILE ]; then
  echo "$KEYFILE already exists, won't overwrite"
  exit 1
fi

$OPENSSL req -new -x509 -nodes -config $OPENSSLCONFIG -out $CERTFILE -keyout $KEYFILE -days 365 || exit 2
chmod 0600 $KEYFILE
echo 
$OPENSSL x509 -subject -fingerprint -noout -in $CERTFILE || exit 2

If you were going to use this certificate for any significant length of time, it would be worth editing the parameters in the config file it uses (/usr/share/dovecot/dovecot-openssl.cnf) to set the proper common name and contact details on the certificate. However, I suggest you leave the defaults as they are, use this certificate just for testing, and then come back later and generate a new cert when everything is working (more on that later).

You must be in the same folder as the configuration file when you run the script, or it will not find the config and the certificate generation will fail. The following two commands will change to the right folder and then execute the script:

cd /usr/share/dovecot
sudo ./mkcert.sh

You should see a message "writing new private key to '/etc/dovecot/private/dovecot.pem'" and then some details about the certificate.

Next, find the following two lines in /etc/dovecot/conf.d/10-ssl.conf and uncomment them:

#ssl_cert = </etc/dovecot/dovecot.pem
#ssl_key = </etc/dovecot/private/dovecot.pem

Now reload dovecot to apply the changes:

sudo service dovecot reload

Since IMAPS is a connection over SSL/TLS, we can’t use Telnet to test it. Instead, we use openssl to create a secure connection. There are two versions of the command, one will show you LOADS of information about the certificate used to encrypt the connection, and the other will suppress this info. I recommend trying the long version out of interest, but both will work the same for the test:

For full information:

openssl s_client -connect localhost:993

For minimal information:

openssl s_client -connect localhost:993 -quiet

I won’t print the output of the first command, because it’s ridiculously long. Here’s an example of the second, including a login test:

admin@samhobbs /etc/dovecot/conf.d $ openssl s_client -connect localhost:993 -quiet
depth=0 O = Dovecot mail server, OU = samhobbs, CN = samhobbs, emailAddress = root@samhobbs.co.uk
verify error:num=18:self signed certificate
verify return:1
depth=0 O = Dovecot mail server, OU = samhobbs, CN = samhobbs, emailAddress = root@samhobbs.co.uk
verify return:1
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
a login "testmail" "test1234"
a OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE] Logged in
b logout
* BYE Logging out
b OK Logout completed.
Connection closed by foreign host.

Good stuff: SSL/TLS is working on port 993, and you can log in successfully.

Note that by default Dovecot uses a “snakeoil” self-signed certificate. SSL/TLS certificates are used for two purposes: encryption and verification. The “snakeoil” certificate will encrypt your content but it won’t verify that you’re talking to your server – you could be talking to someone imitating your server (anyone can create a self-signed certificate claiming to be any website).

If you’d like to get your certificate signed without forking out loads of money to a cert signing authority, I’d recommend CAcert. I've written a tutorial explaining how to generate your own cert and get it signed here. If you opt for a commercial certificate, you can use the CAcert tutorial to generate the certificate and then this tutorial will explain the differences in the installation/configuration of commercial certificates once you have it signed.

If you're testing a proper certificate, use this command to tell openssl where the trusted root certificates are stored:

openssl s_client -connect localhost:993 -quiet -CApath /etc/ssl/certs

Tidying up and enabling WAN access

Before opening the ports on your router to the world, it’s a good idea to delete that test user because the password is so easy to guess.

sudo userdel testmail

Also, if you still use the "pi" login, for goodness' sake change the password from "raspberry"! You can do this using the passwd command when logged in as pi:

passwd

Or you can achieve the same thing when logged in as another user by using sudo to gain root privileges:

sudo passwd pi

Now you can open a few ports on your router’s firewall. Make sure your Pi has a static LAN IP address and then forward these ports from WAN to its LAN IP address:

  • Port 25 for SMTP (used for receiving emails)
  • Port 465 for secure SMTP (used for sending emails after SASL authentication)
  • Port 993 for IMAPS (used to receive emails on your phone/tablet/computer)

Here’s an example on my router, running OpenWrt:

openwrt-port-forwards-raspberry-pi-email-server.png

Setting up IMAP Email Clients

I’m now going to run through setting up IMAP email clients quickly, using K9 Mail on Android and Thunderbird on GNU/Linux as examples. The setup for Thunderbird on Windows and Mac OSX should be very similar.

The basics are this:

  • Select an IMAP connection
  • Your login is your username only (omit @yourdomain.com), and you password is…your password!
  • For incoming emails: select use SSL/TLS always and the program should automatically select port 993
  • For outgoing emails: select SSL/TLS always. The program may suggest port 587, but you want port 465

K9 Mail

Open K9 Mail and select add new account. Type in your account information (you@yourdomain.com and password) and then select manual setup. Select IMAP and then enter your information as follows…

Incoming email:

K9 Incoming Email Settings

Outgoing email:

K9 Outgoing Email Settings

Thunderbird

Open Thunderbird, and then click Account Actions –> Add Mail Account.

Fill in your password and email address, which is your username followed by your fully qualified domain name (FQDN), i.e. username@yourdomain.com:

Thunderbird Step 1: Mail Account Setup

Thunderbird will try to auto-detect settings and fail. Don’t worry, this is normal. Select “manual config”:

 Thunderbird Step 2: TB will try to autodetect settings, and fail. Select “Manual Config"

Now edit the settings as appropriate. I had to remove a period (.) from in front of my “server hostname”, and edit the SSL and Authentication settings. If you select “SSL/TLS” for both incoming and outgoing, ports 993 and 465 are automatically selected:

Thunderbird Step 3: Edit the settings so that they match these (but change them to match your username and domain name!)

Now try emailing yourself from your external email address, and see if your email gets through. If you are having problems, be sure to check you’ve set up an MX record as well as a DNS A record.

Stuck in spam filters?

A few people have contacted me recently to say that their email server is working fine but their emails are getting sent to Gmail's spam folder.

If you are experiencing problems like this (or even if you're not), try setting up an SPF and/or PTR record as explained in my DNS basics tutorial.

You might also want to check if your domain name or IP address are on any blacklists. There's a handy website called MX toolbox that lets you do this (choose blacklist check from the dropdown menu).

Almost done…

Good news! If you’ve reached this far and everything is working, then you’re almost done. The next step (Webmail with Squirrelmail) is optional but by far the easiest of the three steps.

If you’ve hit a rut, please post a comment and I’ll try and help you out.

If not… continue to Raspberry Pi Email Server Part 3: Squirrelmail

Type: 

Comments

Feb 17 11:59:40 pepino dovecot: imap(pi): Error: open(/var/mail/pi) failed: Permission denied (euid=1000(pi) egid=1000(pi) missing +w perm: /var/mail, we're not in group 8(mail), dir owned by 0:8 mode=0775)
Feb 17 11:59:40 pepino dovecot: imap(pi): Error: Failed to autocreate mailbox INBOX: Internal error occurred. Refer to server log for more information. [2019-02-17 11:59:40]
Feb 17 11:59:50 pepino dovecot: imap(pi): Logged out in=155 out=874

I think you've missed the section in part 2 of the tutorial with the heading "Tell Dovecot where your Mailbox is" - dovecot is trying to open your mailbox in /var/mail/pi but it's at /home/pi/Maildir.

If you have the following line:

mail_location = maildir:~/Maildir

but you still have problems, check for duplicates later on that might override it.

Sam

Hi Sam,

Thanks for the terrific guide.

I can receive emails okay, but can't send. I get an immediate error "connecting to Outgoing server (SMTP) chickee.net failed."

Even though I've opened on my router port 465, I can't see it with nmap.

nmap: https://i.imgur.com/EasQVNm.png

NAT: https://i.imgur.com/P3CCMnX.png

greta@3point14159:~ $ ss -nl | grep 465
tcp LISTEN 0 100 127.0.0.1:465 *:*

A few days ago I could send only from my local network (but not while connected to a VPN)... I've done a few other things since then, and now it's not accepting any traffic to chickee.net:465. i can connect using openssl s_client -CApath /etc/ssl/certs -connect localhost:465

I've had a look in the logs and there aren't any clues there.

Any help or assistance is appreciated!

Thank you once again.

Hi,

Do you have another linux machine on your local network? Can you try this openssl test from the other machine:

openssl s_client -CApath /etc/ssl/certs -connect 192.168.1.111:465

If that works but you can't connect from the LAN, we'll know it's probably a firewall/port forwarding/DNS problem.

Sam

Thanks for your reply Sam!

I edited /etc/services and added


smtps 465/tcp smtps ssmtp # SMTP over TLS

and now i get


greta@3point14159:~ $ ss -nl | grep 465
nl UNCONN 0 0 16:465568084 *
tcp LISTEN 0 100 *:465 *:*

and nmap shows


gnealz@nmeal:~> nmap -PS 192.168.1.111
Starting Nmap 7.70 ( https://nmap.org ) at 2019-02-19 09:28 AEDT
Nmap scan report for 192-168-1-111.tpgi.com.au (192.168.1.111)
Host is up (0.75s latency).
Not shown: 994 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
143/tcp open imap
443/tcp open https
465/tcp open smtps
993/tcp open imaps

Nmap done: 1 IP address (1 host up) scanned in 2.22 seconds

When I use


openssl s_client -CApath /etc/ssl/certs -connect 192.168.1.111:465

from my other computer, it connects :))))))))

I can't connect using


openssl s_client -CApath /etc/ssl/certs -connect 110.175.160.170:465

or with the domain name, but i think that's because i have a problem with my registrar (apparently i didn't confirm my email so they deactivated the domain!)

yet i can still connect via SSH to chickee.net...

Hi Sam,

Great tutorial by the way! I was able to go through it properly and successfully test it. When it comes down to the email client like Thunderbird, I keep getting a message that says, "getting a message that the "configuration could not be verified - is the user name or password wrong?".

My question is: can I set this up without a real domain name? Kind of like a test mail server.

Personally, I do have domain name for a blog but I didn't use that domain name on here. I am using ipage for it. If I have to use a real domain name with this, do I have to configure the MX record and DNS record on the raspberry pi or in ipage.com?

Thanks!
Kev

Hi Kev,

You can set it up without the DNS part but you won't receive email from outside (because the DNS record is like the signpost that tells other computers where to send email addressed to yourdomain.com).

DNS records are configured with your DNS provider (presumably that's ipage.com in your case) - see my DNS basics tutorial.

Sam

Hello Sam,

Thank for your great tutorial. Learn a lot.

I followed your instruction all the way through Part 2 (Dovecot) and everything went well (results were exactly as you described). In the end, however, my Thunderbird (on PC and ubuntu) failed to connect.

FYI:
1. on DNS at godaddy.com: A & MX records were set up ok
2. on router with a static IP: port 80, 443, 993,465, 25, 100 were all forwarded to Pi
3. on Pi firewall: ufw allow all ports forward from router
4. on Thunderbird: failed to connect:
Error: Configuration could not be verified - Is username or password wrong?
Note: user: testmail was created, and its mail folder /home/testmail/Maildir
5. on Pi telnet or openssl: the mail did sent through to external server ok
6. on external mail server: mail sent from Pi (via openssl connection) was received ok
7. on external mail server: reply would end up with an error below
Reason: There was an error while attempting to deliver your message with [Subject: "Re: test"] to testmail@profimate.com. MTA p3plsmtpa12-03.prod.phx3.secureserver.net received this response from the destination host IP - 72.167.238.29 - 550 , 550 5.1.1 <testmail@profimate.com> Recipient not found. <http://x.co/irbounce>

Please help. Thanks
Ted

Ted,

Sorry for the late reply. What happens if you send an email to testmail from a local user account on the server?

What do you see in the logs for each case (mail sent from local and remote servers to testmail account)?

Sam

Hi Sam,

First of all: Thanks for sharing your knowledge.

My question is: I managed to setup an email server that is working for some days.
When I send messages to Gmail account is shows a red lock with the message:

"Red (no encryption) No encryption. Unencrypted mail which is not secure. Past messages sent to the recipient's domain are used to predict whether the message you're sending won't be reliably encrypted."

Do you know why? Did I missconfigured something???

Thanks in adavance,

Regards
Odones

Odones,

Sorry it has taken a while to get back to you, I've been really busy. You need to add the following line to main.cf:

smtp_tls_security_level=may

This means your server will use TLS when it can. You can read more here.

Sam

When I try the test under "Testing IMAP", I'm getting to following error.

testmail@raspberrypi:~/Maildir $ telnet localhost 143
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE AUTH=PLAIN AUTH=LOGIN] Dovecot ready.
a login "testmail" "test1234"
* BYE Internal error occurred. Refer to server log for more information.

/var/log/mail.err
May 26 01:03:48 raspberrypi dovecot: imap(testmail): Error: User initialization failed: Namespace '': No home directory for system user. Can't expand ~Maildir for mail root dir in: ~Maildir
May 26 01:03:48 raspberrypi dovecot: imap: Error: Invalid user settings. Refer to server log for more information.

Hi Sam,

This is really an awesome tutorial!

I almost finish the setup but I run into one issue. I can send email from pi to pi, pi to external email address, but pi cannot receive email from external email address. My personal domain name is officialdaniel.com. My public ip address is 174.21.184.64. I check via https://www.canyouseeme.org/ that my 25 is open. I also do `dig officialdaniel.com mx` command and the result is officialdaniel.com as expected. But why I cannot send email from my personal email account to pi@officialdaniel.com?

Thanks a lot,
Daniel

Hi Sam,

First of all, great walkthrough i'm learning so much thanks to you !
The first part went great and now i'm testing the next part.

I have a question thought.

When i try to test the SASL test with telnet i got an error message.

it manage to connect to telnet so i got this :

telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

I can try to ehlo, but nothing happen, more over at some point it close the session with a "Connection closed by foreign host."

I did roll black few steps and notice that when i remove the :

smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes

from main.cf, telnet works fine like in the state of the tutorial first part.

Can you advise on this issue ?

Thanks !

Hi,

Test if postfix is running (sudo service postfix status), you may have a typo in your config file that is preventing postfix from starting.

The other thing that could mess up a telnet connection to port 25 is if the default configuration files shipped by Postfix have changed in a way that requires TLS connections. If you want to test this, then you can try and connect on port 25 using starttls, and see if you get a command prompt:

openssl s_client -starttls smtp -connect localhost:25 -CApath /etc/ssl/certs -quiet

Sam

Evening,

Thanks for the reply

I did try those out and first the service status looks good to me :

● postfix.service - Postfix Mail Transport Agent
Loaded: loaded (/lib/systemd/system/postfix.service; enabled; vendor preset:
Active: active (exited) since Wed 2019-07-17 20:04:09 CEST; 50s ago
Process: 31427 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
Main PID: 31427 (code=exited, status=0/SUCCESS)

Jul 17 20:04:09 raspberrypi systemd[1]: Starting Postfix Mail Transport Agent...
Jul 17 20:04:09 raspberrypi systemd[1]: Started Postfix Mail Transport Agent.

but unfortunately the cmd "openssl s_client -starttls smtp -connect localhost:25 -CApath /etc/ssl/certs -quiet" did not work either :

root@raspberrypi:~# openssl s_client -starttls smtp -connect localhost:25 -CApath /etc/ssl/certs -quiet
Didn't find STARTTLS in server response, trying anyway...
write:errno=32

I did retry to comment the 3 lignes inside the main.cf again and as this, telnet works fine.

Well,

looks like your hunch was right !

root@raspberrypi:~# service dovecot restart
root@raspberrypi:~# sudo service dovecot status
● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; vendor preset: enabled
Active: failed (Result: exit-code) since Thu 2019-07-18 11:26:28 CEST; 1s ago
Docs: man:dovecot(1)
http://wiki2.dovecot.org/
Process: 12607 ExecStart=/usr/sbin/dovecot -F (code=exited, status=89)
Main PID: 12607 (code=exited, status=89)

Jul 18 11:26:28 raspberrypi systemd[1]: Started Dovecot IMAP/POP3 email server.
Jul 18 11:26:28 raspberrypi dovecot[12607]: doveconf: Fatal: Error in configuration fil
Jul 18 11:26:28 raspberrypi systemd[1]: dovecot.service: Main process exited, code=exit
Jul 18 11:26:28 raspberrypi systemd[1]: dovecot.service: Failed with result 'exit-code'

Hi Sam,

I manage to go through the 2nd part :)

Thanks again for you support

Hi Sam!
I installed dovecot and postfix, and I tested my connection with SASL, but cannot work. I don't see "250-AUTH PLAIN LOGIN" when I send telnet command.

pi@rpi3:~ $ telnet localhost 25
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 ordogh.hu ESMTP Postfix (Raspbian)
ehlo facebook.com
250-ordogh.hu
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-DSN
250 SMTPUTF8
auth plain AHRlc3RtYWlsAHRlc3QxMjM0
503 5.5.1 Error: authentication not enabled

I set
/etc/postfix/main.cf
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_auth_enable = yes

10-master.conf
service auth {
unix_listener /var/spool/postfix/private/auth {
mode = 0660
user = postfix
group = postfix
}
}

and
10-auth.conf
disable_plaintext_auth = no
auth_mechanisms = plain login

Please help, I have no idea.

Attila,

Is dovecot running?

Is authentication offered on port 465 (use openssl to connect as described later in the tutorial)?

Sam

Yes, dovecot is running. Ports enabled in router, and I set dovecot like you wrote. I didn't installed email client yet.
Error is the same.

First off, thank you for making this, and thank you for keeping it up all these years! nearly 40 pages of comments makes it hard to sift through for problems similar to my own, though.

So, i'm pretty sure i set everything up correctly. Fixed the few errors that were popping up because i accidentally added a space to one of the "-o smt [blagh]" things in master.cf.
Thunderbird connects, and i can even click "send" on an email and thunderbird *says* it's been sent.
But nothing's going out. And anything i try to send from gmail doesn't get in either.

all the ports are forwarded correctly, all that stuff works as far as i can tell, but this part doesn't.

Have you tried any other email clients? Thunderbird has become a bit temperamental since Mozilla stopped actively developing it.

If you've done that, try watching the logs as you send an email and see what happens (do you see a connection from the client?).

If not, it could be a firewall thing (e.g. port forwarding), a DNS issue or a misconfiguration (is postfix running?).

Sam

Thanks for this Sam, bet you're glad you wrote it so long ago and here is hoping you are still answering queries.

I have followed the guide from the start and am at the section for;
Now try openssl:

openssl s_client -connect localhost:465 -quiet

I get
Can't use SSL_get_servername
depth=0 CN = email-pi
verify error:num=18:self signed certificate
verify return:1
depth=0 CN = email-pi
verify return:1
220 itsnotsecure.com ESMTP Postfix (Raspbian)

email-pi is my hostname, not my email name. I have checked the postfix/main.cf and postfix/master.cf and cannot see the error. Any clues / thoughts?

Many thanks,
Chris

Chris,

The common name is on the certificate, which at the moment should be the default cert automatically generated during the installation of postfix (which uses your hostname as the common name).

You can replace the certificate with a new one with your domain name on it. Nowadays I'd recommend LetsEncrypt - it's free and there are great tutorials for certbot, the software that generates the certificate and gets it signed (see here).

Sam

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