This guide is part 1 of what I plan will be a couple of guides that take you through installing a base mail system, SpamAssassin, DKIM and much more. Stay tuned.
This guide was written for Debian 6 but should be the same or similar for Debian 5 and Ubuntu 10.04 and above.
The installation
sudo apt-get install dovecot-imapd postfix sasl2-bin libsasl2-2 libsasl2-modules
Choose “Internet site” when prompted and enter the fully qualified name of your server.
Once all this is done installing we’ll need to make some changes, first off will be Postfix.
Postfix
Open up /etc/postfix/main.cf and add the following to the end of the file
home_mailbox = Maildir/
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
broken_sasl_auth_clients = yes
smtpd_sender_restrictions = permit_sasl_authenticated,
permit_mynetworks,
smtpd_recipient_restrictions = permit_mynetworks,
permit_sasl_authenticated,
reject_unauth_destination,
reject_unknown_sender_domain,
Here we basically tell Postfix to store all email in maildir format in the user’s home directory. We then enable SASL with and tell it to not allow anonymous auth and, tell it the hostname and enabled broken SASL auth clients, just in-case.
The next section tells Postfix to allow users to send if they pass SASL auth or are listed in the allowed networks section.
Finally we set Postfix’s recipient rules where we allow our networks, SASL auth and reject any unauthorised destinations and unknown senders.
Dovecot
Open up /etc/dovecot/dovecot.conf
Uncomment the IMAP and IMAPS protocols
protocols = imap imaps
Next we configure the protocols, add the following lines just below the protocols option
protocol imap {
listen = *:143
ssl_listen = *:993/
}
Search through the file for “mail_location =” without the quotes, make sure it’s commented out and add the following below it:
mail_location = maildir:~/Maildir/
Now we need to search down the file and comment out everything within the “auth default” section and add the following below it
auth default {
mechanisms = plain login
passdb pam {
}
userdb passwd {
}
socket listen {
client {
path = /var/spool/postfix/private/auth
mode = 0660
user = postfix
group = postfix
}
}
}
Just to explain what we’ve done, we’ve enabled IMAP and IMAPS protocols and configured the ports to be used, both ports are the standard ports.
Next up we configure Dovecot to handle Maildir, just like with Postfix.
And finally we set up our auth mechanism, specifying that it needs to do so via Postfix.
SASL
Open up the following file**/etc/default/saslauthd**, we need to modify a couple of things. Set START to yes and MECHANISMS to pam.
START=yes
MECHANISMS="pam"
Due to the fact Postfix will be chrooted we need to make a few system changes for SASL.
First we remove the default SASL run location.
sudo rm -r /var/run/saslauthd/
Now we make one within the Postfix chroot.
sudo mkdir -p /var/spool/postfix/var/run/saslauthd
Symlink it back to /var/run so things work.
sudo ln -s /var/spool/postfix/var/run/saslauthd /var/run
Change the group for the directory we created.
sudo chgrp sasl /var/spool/postfix/var/run/saslauthd
And finally add the Postfix user to the SASL group.
sudo adduser postfix sasl
Finally
Now we just need to restart our services.
sudo /etc/init.d/dovecot restart
sudo /etc/init.d/postfix restart
sudo /etc/init.d/saslauthd restart
If all went according to plan normal system users should now be able to send and receive mail.
