doveadm backup from gmail with imapc

[Plutocrat]

On 08/04/2020 19.14, Ben Mulvihill wrote:
> Thanks for the suggestion. I think my next step will be to investigate
> imapsync, or maybe isync, which also looks promising.

I've recently migrated a server with imapsync with 150Gb of email and 200+ accounts. I found the trick with this was the run imapsync in several runs: Messages older than 1 year; messages older than 6 months; messages older than 1 week, for example. Then just keep running the full sync after that until you're ready to switch. If you've just got one email then this should be easy. With many addresses, there is a bit of scripting to do first to get it all set up. 

One gotcha, which I never solved, (mainly due to the fact I had to do the whole migration in under a week as an emergency). I could never figure out how to get the dovecot indexes correct, so that when the client connected to the new server via POP, it didn't re-download all the messages. IMAP was OK though. 

P.