There are easier ways, but it depends on how comfortable you are with email stuff and how flexible your email hosting setups are. I host my own email servers,

There are easier ways, but it depends on how comfortable you are with email stuff and how flexible your email hosting setups are. I host my own email servers, so when people are migrating accounts in, what I've done is set up their accounts to use fetchmail to fetch email from the previous provider when the previous provider offers no direct access. Some providers can allow you direct access to your mail spool file, so rsyncing that across is easiest. If you set the TTL on DNS to really low, like half an hour, a week before the actual move, you'll have a very small window in which email might go to either the new place or the old place. There are ways to make sure there's absolutely no overlap, if that's a big deal, but for most things this works just fine. If the email mostly lives on the client and you don't care about syncing mailboxes on the server, just configure the email clients to check both the old and new servers for a few days, then remove the old server when you're 100% sure nothing is going there any more.