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

Yes, they are blocking. :-( Connection timed out.
Can I make something,for example email relay or other thing? I want to make my CaCert, but i cannot because i cannot get the mails.

Hi Sam,
I just restored a image of my pi, but now my mails bounce with the message: mail for "mydomain" loops back to myself.
Please help... need a rescue for for my rescue:)

Are you sure the config files were restored to their "finished" state? If you're trying to send mail between two local users, the server should know it is a destination for yourdomain.com because of the mydestination parameter (so postfix shoudn't get into a loop where it looks up the DNS record for yourdomain.com and ends up contacting itself).

Sam

Hi Sam,

Before all,

Thanks you very much for your tutorials, they help me a lot to configure my server (email, web and others).

Unfortunately, with my email server I can send but not receive any email. Below some results after my tests:

The answer in the "Delivery Status Notification (Failure)" email:
Technical details of permanent failure:
DNS Error: 127165 DNS type 'mx' lookup of icos.ch responded with code NOERROR
127165 DNS type 'aaaa' lookup of mail.icos.ch. responded with code NXDOMAIN
127165 DNS type 'a' lookup of mail.icos.ch. responded with code NXDOMAIN

When I test on MXToolbox site:
SMTP Banner Check: Reverse DNS does not match SMTP Banner
In the more info page: "If you do not have a PTR record, or your record does not match your hostname, we recommend that you contact your ISP and ask them to setup a reverse (PTR) record that matches the hostname of your mail server."

But in my /etc/postfix/main.cf there is:
smtpd_banner = $myhostname
myhostname = icos.ch

And in my FreeDNS registration there is an MX Record:
Type: MX
Domain: icos.ch (public)
Destination: 10:mail.icos.ch

What do you think? I need to ask at my ISP to setup a reverse (PTR) record?

Thanks in advance for your answer and have a nice day.

David

Hi David,

You have an MX record, but no DNS A record for the subdomain you have specified. Here's the MX record:

sam@T440s:~/git/hangish$ dig +short icos.ch mx
10 mail.icos.ch.

But no A record:

sam@T440s:~/git/hangish$ dig +short mail.icos.ch

You do have an A record for icos.ch though, did you mean to put that in your MX record?

sam@T440s:~/git/hangish$ dig +short icos.ch
83.172.215.245

A PTR record will help ensure your messages aren't treated as spam, so you should definitely try and change yours if you can.

Here's my DNS tutorial in case you missed it.

Sam

Thanks Sam.
I followed your tutorial for DNS, and my ISP added a PTR to mail.icos.ch and I get emails now, but in / var / mail / dissen0d and not in / home / dissen0d / Maidir
I certainly missed something in your mail server tutorial, I will follow another time your tutorial.
Thanks for your help.

Right at the start of part 2, there's a heading called "tell Dovecot where your mailbox is". Lots of people miss that. Make sure the line isn't in your configuration twice (if you have the same line twice, the one read last overrides the first).

Sam

Hi Sam,

Thanks for your answer. In fact, I have check if this line (mail_location = maildir:~/Maildir) was present, and it was the case. looking for another solution, I have found on another forum that we need to add this line "home_mailbox = Maildir/" in postfix/main.cf. I have added, and it works.

Thanks for all, because your tutorials are very helpful.

See you.

Nice job. Everything worked just as you had documented. I configured the mail services on the same Raspberry that runs WordPress (presspi) so I wasn't sure it would all operate together and it did without a hitch. Great leadership you guys!

Please help! I went through the tutorial successfully (or at least I thought so). I had a few stumbles, but got to a point where I could set up an email account. The email appears to be sent, however...no email received, also cannot receive emails. I believe it is a dns/mx record issue, but ??

Ok, I can read the incoming messages on the pi itself at /home/Maildir/new, however the email client is not displaying any messages. I checked the settings many times, and 'Thunderbird' seems to be connecting to my pi normally. It seems Thunderbird is not looking in the right place for the emails? Any ideas?

Hmm... have a look in the logs and see if you can verify that Thunderbird is connecting to the right server, and we'll go from there!

The log is at /var/log/mail.log.

Sam

Hello again Sam, thanks for the reply. Checking the mail.log, it seems Thunderbird is not connecting to my server. Although I'm not sure how to tell for sure? More troubling, I actually see a few 'unknown' connections coming from an unrecognized IP, only connecting for 30 seconds or so. Not sure what's going on there, but?? Maybe time to close the ports on my router?

I think you're probably right about it being a DNS issue then, did you read the DNS tutorial?

I wouldn't worry about random connection attempts unless there are lots of authentication failures (and then that's what fail2ban is for).

Sam

Hello Sam, thanks for the information. I think the symptoms I am having are kinda odd. I can see incoming mail in my /home/Maildir directory, I can see in the mail log when Thunderbird connects to my server, I also see in the mail log attempts to connect to google's mail server and failing "Connection timed out" "No route to host". I'm running out of ideas.

Rob,

Some things to check:

  • You are using the same account (i.e. you see mail in /home/rob/Maildir and you are trying to connect with the rob@yourdomain.com account in Thunderbird).
  • The Maildir is owned by rob:rob with permissions 700. No errors about permission in the mail log.
  • At least some of the messages in the Maildir are from external email addresses, not just local test emails (if no external email has been received, then it may still be a DNS problem and the inbox you are logging into with thunderbird might be on a different server).
  • You can see messages in the inbox when you test connecting to port 993 manually with openssl s_client using the domain name of the server (not localhost). Check you don't get different results for localhost and yourdomain.com

The connection timed out messages indicate that your ISP is blocking port 25 outbound... that's a different problem though, let's sort this one first.

Sam

Hello again Sam, I am using the same account. It's actually the 'pi' account (just for testing of course). The mail I see is actually in /home/pi/Maildir/new.
I do have the permissions on the directory 'drwx-------' something like that. 'pi : pi'
Yes, I am seeing messages from my gmail account.

I did ssl into the server using my domain name, however at the 'dovecot ready' prompt I'm not sure what to type. It logs me out after a couple minutes. I see the long certificate displayed when I log in.

?? Any ideas would be great. Rob

Hello again Sam, one other question on the side I have is,,,when it comes to FQDN's, for example, in the postfix/main.cf file for 'myhostname' I should have the name of my email server.mydomainname? and in the MX record it should be the same or just my domain name? (ie robsserver.robsdomain.com) or just robsdomain.com? Thanks, Rob

Hello Sam, I found one issue, there was an error in the 10-mail.conf file, where it tells dovecot where my inbox is. Now I need to find out why I cannot send mail. Thanks for your help. Rob

Hello again Sam, picking this up again after the holidays...
I can now receive mail, there was a second line indicating my mailbox location that was incorrect. Deleted it, all is fine.
However, I still cannot send mail, maybe this is because my ISP is blocking port 25? Is there a way to get around this?
Or first, a way to confirm this is the reason I cannot send mail?

Thanks again, Rob

Hello Master Hobbs,
I call you that because you must be some kind of programming genius to have come up with this!! I want to thank you very much for posting these steps. I have just started web programming about a year ago and have created a simple website that allows me to test various programming stuff and am looking to add email so this tutorial was perfect.

I am, however, having an issue when I attemp the IMAP setup. When attempting to add my account in Thunderbird it is stating that it failed to find the setting for my email account.

I am using Thunderbird on my Windows 7 Professional machine.

I purchased the domain name from Google Domains and have verified that I have a correct A record and MX record:

david@pi-mailserver:~ $ dig johndavidhock.net

; <<>> DiG 9.9.5-9+deb8u8-Raspbian <<>> johndavidhock.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5915
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;johndavidhock.net. IN A

;; ANSWER SECTION:
johndavidhock.net. 2471 IN A 68.184.112.150

;; Query time: 1 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Tue Jan 03 06:08:24 UTC 2017
;; MSG SIZE rcvd: 62

david@pi-mailserver:~ $ dig johndavidhock.net mx

; <<>> DiG 9.9.5-9+deb8u8-Raspbian <<>> johndavidhock.net mx
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22970
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;johndavidhock.net. IN MX

;; ANSWER SECTION:
johndavidhock.net. 3254 IN MX 10 johndavidhock.net.

;; Query time: 25 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Tue Jan 03 06:08:31 UTC 2017
;; MSG SIZE rcvd: 62

Do you have any ideas on what I could be doing wrong?

Thanks very much for your assistance,

Dave Hock

What do you mean "failed to find the setting", does that just mean it didn't automatically detect which ports to use etc.? If so, you should be able to select them manually.

I don't know how (maybe it's a preset that is shipped with TB) but for some account providers like gmail, TB knows the ports etc. to use without being told.

Sam

# openssl s_client -connect localhost:587 -quiet
139903608960664:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:s23_clnt.c:794:

Is there something I am missing in the config Sam?
P.s I am using Ubuntu 16.04 and not the raspi

Hi Sam
I am not able to telnet port 465. I am able to send mail from my mail server to gmail but the messages are not coming to my inbox when i am sending the mails from gmail to my user.

You probably have a DNS problem, did you follow the DNS tutorial?

When you say you can't telnet to port 465, do you mean you can't connect with telnet or openssl? Once you force tls wrappermode on port 465, you need to connect using openssl.

Sam

Hello,

I was wondering if its possible to receive all emails if my port 25 is blocked by my router?

Yesterday I got a new router and it blocks some ports by default including 25....

Regards,

Stefan de Raadt

Hi Stefan,

No, unfortunately you can't receive email if port 25 is blocked. Is the router supplied by your ISP? You can usually change the settings on the router using the admin interface, but if this one won't let you you can always put it in bridge mode so it acts as a modem, and then connect it to your old router which will do the routing.

Sam

P.S. Are you related to OpenBSD's Theo de Raadt?

Hello Sam,

Sadly I just can't set the port to 25 its in a blocked list for some reason. The old router was also from my ISP and has been send back.... I think I'm going to get a new one to do the routing for me then.

I'm not related to Theo de Raadt I think. Its funny that he has the same last name as me haha.

Thanks for the fast reply!

Regards,

Stefan de Raadt

If you're looking at routers, I recommend getting one with good support for OpenWrt.

Mine is a TP-Link WDR-3600, which is good and pretty cheap, but there are loads of others too.

Good luck :)

Sam

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