Configure exim4 internet site; mail is sent and received directly using SMTP

This option of exim4 let you configure SMTP server for your domain.

• SMTP host FQDN: mail1.dev.local, ip: 192.168.10.11
• Domain: dev.local, serves emails like user1@dev.local
• Delivery mode: Maildir
• Mail location: /var/mail/<user>

Here are few simple steps to configure:

1. Let install the 'heavy' version of exim4:

   apt-get -y install exim4-daemon-heavy
   

2. The easiest way is to reconfigure exim4-config package:

   dpkg-reconfigure exim4-config
   

3. General type of mail configuration:
      internet site; mail is sent and received directly...
   System mail name:
      dev.local
   IP-addresses to listen on for incoming SMTP connections:
      192.168.10.11
   Other destinations for which mail is accepted:
      dev.local
   Domains to relay mail for:
   
   Machines to relay mail for:
      192.168.10.0/24
   Keep number of DNS-queries minimal (Dial-on-Demand)?
      No
   Delivery method for local mail:
      Maildir format in home directory
   Split configuration into small files?
      Yes
   

4. Since we want to change default Maildir delivery to /var/mail/<user>, let add our custom local delivery rule (file /etc/exim4/update-exim4.conf.conf):

   #dc_localdelivery='maildir_home'
   dc_localdelivery='maildir_spool'
   

5. Consider disable IPv6 (file /etc/exim4/update-exim4.conf.conf):

   disable_ipv6='true'
   

6. Make a copy of existing Maildir rule file:

   cp /etc/exim4/conf.d/transport/30_exim4-config_maildir_\
   {home,spool}
   

7. Change configuration for maildir_spool transport (file /etc/exim4/conf.d/transport/30_exim4-config_maildir_spool):

   ### transport/30_exim4-config_maildir_spool
   #################################
   
   maildir_spool:
     debug_print = "T: maildir_spool for $local_part@$domain"
     driver = appendfile
     .ifdef MAILDIR_HOME_MAILDIR_LOCATION
     directory = MAILDIR_HOME_MAILDIR_LOCATION
     .else
     directory = /var/mail/$local_part
     .endif
     .ifdef MAILDIR_HOME_CREATE_DIRECTORY
     create_directory
     .endif
     .ifdef MAILDIR_HOME_CREATE_FILE
     create_file = MAILDIR_HOME_CREATE_FILE
     .endif
     delivery_date_add
     envelope_to_add
     return_path_add
     maildir_format
     .ifdef MAILDIR_HOME_DIRECTORY_MODE
     directory_mode = MAILDIR_HOME_DIRECTORY_MODE
     .else
     directory_mode = 0700
     .endif
     .ifdef MAILDIR_HOME_MODE
     mode = MAILDIR_HOME_MODE
     .else
     mode = 0600
     .endif
     mode_fail_narrower = false
     current_directory = /var/mail
     group = mail
   

8. Restart exim4:

   /etc/init.d/exim4 restart
   

Let verify it is working:

echo "test message" | mail -s "test" user1

... exim4 log (file /var/log/exim4/mainlog):

1PpRQR-0002Rz-1m <= root@dev.local U=root P=local S=460
1PpRQR-0002Rz-1m => user1  R=local_user T=maildir_spool
1PpRQR-0002Rz-1m Completed

At this point user1 should be able to receive your test message.