Cfrtjryk

I am migrating a mailserver running sendmail 8.14.3 to a postfix server. The MDA on the new server is Dovecot. In order to ensure a seamless transition, it would be best if incoming mails are delivered to both servers simultaneously.

I've heard about the SMART_HOST and nullcient options in sendmail, but I'm not sure if this works in the way I need it to. What I need is all incoming mails also delivered to the new server, leaving the existing configuration untouched, as they should be delivered to the mailboxes on the old server as well.

Mails are sent to an address like test@mydomain.com and should be delivered to mx1.mydomain.com (old) and mx2.mydomain.com (new). So mx1 should forward a copy to mx2.

Dual MX Records are not enough as the one server would only be contacted when the other one isn't reachable - while both should be receiving the mail.

Maybe another option would be to configure sendmail to deliver directly to Dovecot on the new server via lmtp? Or maybe just rsync the mailboxes on the two servers. But I'm not sure if that's compatible.

UPDATE: It's not the same format: on the old server, there are just plain old files for each mailbox, while Dovecot creates a cur, new tmp structure in each user's mail directory. However, in the end, files with a similar format reside in those directories. The speration string is different though. Maybe it's possible to translate the old format and copy it to the new server periodically? Would that somehow interfere with Dovecot? And where could I place the copies on the new server so that Dovecot won't be affected while still recognising them?

I hope there is some kind of workaround for that.

System Indormation

Number of mailboxes: ~100-200

Old Server:

OS: Debian GNU/Linux 6.0

sendmail 8.14.3

mails are delivered to "real"/"passwd" users

Other Serives: apache2, mysql, other miscellaneous

New Server:

OS: Debian GNU/Linux 9

postfix

dovecot

mails are delivered to virtual users/SQL

Other services: apache2, mysql, other miscellaneous

Current MX entry for reference:

mydomain.com.    IN      MX      0 mx1.mydomain.com.

mydomain.com.    IN      MX      1 mx2.mydomain.com.

I can't test this right now but I'm fairly sure sendmail understands entries in /etc/aliases of the form

fred: fred, fred@otherserver

(If it goes into a mad loop, prefix the second fred with a backslash .)

Then it's a straightforward extract from /etc/passwd into the aliases file. And remember to run newaliases (?) to update the internal sendmail database.

Here is an example snippet to generate the lines that would be appended. It considers only users whose UID is in the range { 1000 ≤ uid < 65000 }.

[ ! -f /etc/aliases.save ] && cp -p /etc/aliases /etc/aliases.save



(

    cat /etc/aliases.save

    echo

    getent passwd |

        awk -F: '$3>=1000 && $3<65000 {printf "%s: %s, %s@mx2.mydomain.comn", $1, $1, $1}'

) >/etc/aliases



newaliases