Hi!
I fear this may be slightly off-topic but it's both related to IMAP and to dovecot:
Is there any good and in paticular realiable program for synching / migrating one IMAP mailbox to another? The most important features for me is that a) no mails are lost / left out silently and b) the porgram is able to sync the complete mailbox including all folders without just giving up in the middle of the transfer. If it's somehow possible, I'd like to migrate directly from one IMAP account to the other, without running the synchronizer on one of the servers and without accessing one of the Maildirs directly.
I simply want to migrate my existing IMAP account from one Dovecot server (running 1.0beta5) to a new one (running 1.0rc15, as that's the version in Debian stable). Actually, a large part of the mailbox including most / all folders is already present on both servers, but I recently noticed that a few thousand mails are still missing.
The current mailbox state is the result of two earlier (obviously incomplete :-( ) migrations a few months ago, from the original Dovecot 1.0beta5 server to a Cyrus server, and - shortly thereafter - from there on to the currently used Dovecot 1.0rc15.
So far I've tried offlineimap, imapsync and mailsync, none of which seems to be really usuable. :-(
The current state with the incomplete mailbox was caused by mailsync. When I did the first two migrations, mailsync looked like the only program which worked, but seems to have "forgotten" the missing messages. Another extremely suspicious thing is that mailsync reports "phantom changes" if run again immediately after synching a folder and will start to delete and copy / "sync" dozends of messages even if none of the folders actually changed after synching.
I've read the name "imapsync" on this list several times, but I just tried it and just tried version 1.219. It happily starts synching the mailboxes and copying messages, but stops after partially synching the first folder - it simply exists, leaving no informational or error message whatsoever... Restarting imapsync will not help, it will appear to start synching the first folder again, but silently exit without doing anything. Some of you seem to use imapsync as a migration tool for production systems, how do you cope with these situations and how do you ensure a mailboxs' migration actually completed successfully? As you're probably not playing Roulette with your customers' or companie's eMails, I'm interested in your receipts to successfully use imapsync myself.
As the third application I tried offlineimap (4.0.x-branch). During the migration a few months ago offlineimap (4.0.16 IIRC, synching from a Maildir to a remote IMAP account) was unusuable as it continuously and reproducibly threw exceptions at me during syncing obviously caused by specific messages in the accounts. Unfortunately, I wasn't able ti get any successful help on the offlineimap mailing list this time. :-(
Now, synching from one IMAP account to another, specifiying the new server as the "local" account, offlineimap did not throw exceptions caused by mail messages so far, but it's performance is unusuable. It seems to use the "local" IMAP account on my target sevrer in a way which causes Dovecot to utilize all CPU power, copying one message every 10 to 20 seconds - this way, a sync would take ages and frequently aborts because of connection problems. The target server is an Athlon64 3700+ machine...
So, does anyone have any pratical solution on how to migrate one IMAP mailbox to another? For various reasons I'd really prefer to go with a tested and working, reliable solution instead of starting to debug complex non-working programs I do not halfway understand and for which I cannot seem to get reliably support from its authors and/or its user community... :-/
Thanks a lot in advance for any pointers to a solution,
Gunter
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