Install Dovecot
To install a basic Dovecot server with common POP3 and IMAP functions, run the following command:
sudo apt install dovecot-imapd dovecot-pop3d
There are various other Dovecot modules including dovecot-sieve (mail filtering), dovecot-solr (full text search), dovecot-antispam (spam filter training), dovecot-ldap (user directory).
Configure Dovecot
To configure Dovecot, edit the file /etc/dovecot/dovecot.conf and its included config files in /etc/dovecot/conf.d/. By default, all installed protocols will be enabled via an include directive in /etc/dovecot/dovecot.conf.
!include_try /usr/share/dovecot/protocols.d/*.protocol
IMAPS and POP3S are more secure because they use SSL encryption to connect. A basic self-signed SSL certificate is automatically set up by package ssl-cert and used by Dovecot in /etc/dovecot/conf.d/10-ssl.conf.
Mbox format is configured by default, but you can also use Maildir if required. More details can be found in the comments in /etc/dovecot/conf.d/10-mail.conf. Also see the Dovecot web site to learn about further benefits and details.
Make sure to also configure your chosen Mail Transport Agent (MTA) to transfer the incoming mail to the selected type of mailbox.
Restart the Dovecot daemon
Once you have configured Dovecot, restart its daemon in order to test your setup using the following command:
sudo service dovecot restart
Try to log in with the commands telnet localhost pop3 (for POP3) or telnet localhost imap2 (for IMAP). You should see something like the following:
bhuvan@rainbow:~$ telnet localhost pop3
Trying 127.0.0.1...
Connected to localhost.localdomain.
Escape character is '^]'.
+OK Dovecot ready.
Dovecot SSL configuration
By default, Dovecot is configured to use SSL automatically using the package ssl-cert which provides a self signed certificate.
You can instead generate your own custom certificate for Dovecot using openssh, for example:
sudo openssl req -new -x509 -days 1000 -nodes -out "/etc/dovecot/dovecot.pem" \
-keyout "/etc/dovecot/private/dovecot.pem"
Next, edit /etc/dovecot/conf.d/10-ssl.conf and amend following lines to specify that Dovecot should use these custom certificates :
ssl_cert = </etc/dovecot/private/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.key
You can get the SSL certificate from a Certificate Issuing Authority or you can create self-signed one. Once you create the certificate, you will have a key file and a certificate file that you want to make known in the config shown above.
Further reading:
For more details on creating custom certificates, see our guide on security certificates.
Configure a firewall for an email server
To access your mail server from another computer, you must configure your firewall to allow connections to the server on the necessary ports.
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IMAP - 143
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IMAPS - 993
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POP3 - 110
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POP3S - 995
References
- The Dovecot website has more general information about Dovecot.
- The Dovecot manual provides full documentation for Dovecot use.
- The Dovecot Ubuntu Wiki page has more details on configuration.