local stanza only generated for IPv6

[Jeremy Ardley]

Further to my report on stanzas being only generated the IPv6 addresses
I have found a work-around until someone in the development team comes
up with something like inet_listener_6 and inet_listener_4

The workaround is simply to get dovecot to listen in IPv4 and IPv6. It
has no effect on clients who will use ordinary MX records to access the
normal mailserver name

The workaround requires modifying DNS with duplicate A and AAAA records
(not CNAME or ALIAS) for the addresses of interest. So in the instance
of one domain:

mail    A       192.168.0.1
        AAAA    2001:0db8:85a3:0000:0000:8a2e:0370:7334

mail4   A       192.168.0.1

mail6   AAAA    2001:0db8:85a3:0000:0000:8a2e:0370:7334

Then the dovecot.conf file requires multiple local stanzas. In this case
two domains requires four stanzas

listen =
mail4.example.com,mail6.example.com,mail4.example2.com,mail6.example2.com,localhost

protocols = imap lmtp sieve

ssl_min_protocol = TLSv1.2
ssl_cipher_list = EECDH+AESGCM:EDH+AESGCM
ssl_prefer_server_ciphers = yes

local mail4.example.com {
  protocol imap {
     ssl_cert = </etc/letsencrypt/live/mail.example.com/fullchain.pem
     ssl_key = </etc/letsencrypt/live/mail.example.com/privkey.pem

     service imaps_login_4 {
       inet_listener imaps {
         address=mail4.example.com
       }
       inet_listener imap {
         address=mail4.example.com
       }
     }
  }
}

local mail6.example.com {
  protocol imap {
     ssl_cert = </etc/letsencrypt/live/mail.example.com/fullchain.pem
     ssl_key = </etc/letsencrypt/live/mail.example.com/privkey.pem

     service imaps_login_6 {
       inet_listener imaps {
         address=mail6.example.com
       }
       inet_listener imap {
         address=mail6.example.com
       }
     }
  }
}


local mail4.example2.com {
  protocol imap {
    ssl_cert = </etc/letsencrypt/live/example2.com/fullchain.pem
    ssl_key = </etc/letsencrypt/live/example2.com/privkey.pem

    service imaps_login_44 {
      inet_listener imaps {
         address = mail4.example2.com
      }
      inet_listener imap {
         address = mail4.example2.com
      }
    }
  }
}

local mail6.example2.com {
  protocol imap {
    ssl_cert = </etc/letsencrypt/live/example2.com/fullchain.pem
    ssl_key = </etc/letsencrypt/live/example2.com/privkey.pem

    service imaps_login_66 {
      inet_listener imaps {
         address = mail6.example2.com
      }
      inet_listener imap {
         address = mail6.example2.com
      }
    }
  }
}