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Andras
Asked: 2022-05-18 00:14:43 +0800 CST

What is the Best Practice to switch between Old and New Email Server to minimize outage?

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I have been using self built email servers for years now on Ubuntu Server with Postfix + Dovecot.

Once before, I have decided to build a newer email server, and I called it by a different Fully Qualified Domain Name than the Old Server was called. Then of course when the moment of switch over came, I had to alter the Resource Records (A, PTR and MX) in my domain (and at my ISP) to make the switch between the two servers.

The way I remember now, it is something like it wasn't really a smooth switchover, even though I have prepared all the involved Resource Records to have 1min TTL set for a while, it just didn't work straight away, without sweating a lot :).

Also nearly every single email within one folder of emails seem to be contained in a single file surrounded by all sorts of hash and checksum looking data, that made me a little frightend to copy emails from the Old Server to the New Server by linux file transfer. So, at the end I realised, that once I had both servers hooked up to Thunderbird through IMAP, actualy both containing the same account, I could just drag & drop all my folders from the Old Server to the New Server.

How do experineced people change over to a New Email Server?

email

1 Answers

  1. During my last successful migration project, I used dovecot replicator. It can transparently replicate mailboxes between two servers, no data loss. You can take your time between the following steps, 0 stress:

    1. Set up the new server as a replicator.
    2. At this point, your old server will still receive all traffic so let the replication from the old server to your new server run for a while.
    3. Force all incomming (LMTP) and IMAP/POP session to the new server. Best use dovecot director.
    4. At some point, replication will be from the new server to the old server. Only then, you can get rid of the old server or keep it as backup.

    Note: Replication is not real time but depending on your hardware and network it can be close to it.

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