On 3/8/2019 4:44 AM, Voytek Eymont via dovecot wrote:

I have Centos 7 with dovecot/postfix/mysql Maildir

I want to bring in a new server, new server will have same hostname as current, but, different IP

I was intending to rsync -avzhe ssh vmail@oldserver:/var/vmail/vmail1 /var/vmail/vmail1

and, then, re run as necessary when/if mail still arrives on old server

is that "a good plan" ...?

What I did when I migrated my mail service to a new server:

Preparatory steps:

• Made sure new server was set up.
• Tested functionality on new server as much as I could.
• Did occasional rsyncs (-avH --delete) of mail content from old server to new server.

Three days before go time, I did this:

• Lowered the DNS TTL value for imap and smtp records to 300.
• Waited 3 days to be sure that TTL had penetrated the whole Internet.

On the day of the migration, these were the steps I followed.

• Shut down postfix and dovecot on both old and new servers.
• Updated DNS records to point to new address.
• Ran one final rsync of maildirs from old server to new server.
• Waited 30 minutes with services on both servers still shut down.
• Started postfix and dovecot on new server.

At this point you can set the DNS TTL back to a larger value, if you wish.

I waited 30 minutes just to be absolutely sure that the DNS change had propagated everywhere. Ten minutes probably would have been enough; I was just being cautious.

If you plan to keep the old server without doing a fresh OS install, it's a good idea to wait a few days before restarting services on it. In my case, I removed dovecot and reconfigured postfix on that machine to be a satellite system relaying to the new server.

Thanks, Shawn