Hi,

I'm experiencing serious issues using doveadm sync; mails are not replicating and/or mails are duplicating. I wanted to use this for migrating external mailboxes to my server (in order to overcome the time when some servers/clients still use the old server and some already my server, as described on <https://wiki2.dovecot.org/Tools/Doveadm/Sync>).

Finally I was able to reproduce this with the 2.3 branch (cf. <https://dovecot.org/pipermail/dovecot/2019-April/115600.html>). I'm sorry that I can only test the version 2.3.4.1, but according to the changelog I think this is still an issue with the latest version.

I tried to find a few steps in order to replicate this easily: For testing purposes I simulate both the remote and local server on my Dovecot instance. I created remote@DOMAIN.TLD and local@DOMAIN.TLD accounts and both use mdbox and are empty.

First, send two mails to remote@DOMAIL.TLD (Subjects: Test1 and Test2).

Start backup remote IMAP account (remote@DOMAIN.TLD) to local account (local@DOMAIN.TLD): $ doveadm -o imapc_user="remote@DOMAIN.TLD" -o imapc_password="PW" -o imapc_host="localhost" backup -R -u local@DOMAIN.TLD imapc:

Both mailboxes are in sync now (containing Test1 und Test2).

Now send two messages to remote@DOMAIN.TLD (Subjects Test3 and Test4) and two messages to local@DOMAIN.TLD (Subjects Test5 and Test6).

Run sync: $ doveadm -o imapc_user="remote@DOMAIN.TLD" -o imapc_password="PW" -o imapc_host="localhost" sync -R -u local@DOMAIN.TLD imapc:

See that syncing fails: remote@DOMAIN.TLD contains: Test1,2,3,4,5,6 (as expected) local@DOMAIN.TLD contains: Test1,2,5,6,4 (Test3 is missing here) When not using the "-R" parameter it seems to work.

Running sync again: $ doveadm -o imapc_user="remote@DOMAIN.TLD" -o imapc_password="PW" -o imapc_host="localhost" sync -R -u local@DOMAIN.TLD imapc: causes messages to duplicate: remote@DOMAIN.TLD contains: Test1,2,6,5,4,3,5,6,4,6,5,4,3,5,6 local@DOMAIN.TLD contains: Test1,2,5,4,6,4,5,6 (3 is still missing) This is independent of the "-R" parameter.

I could also experience this issue when using one-way sync, however, the first one-way sync is still ok, but then messages start duplicating as for the two-way sync without "-R": $ doveadm -o imapc_user="remote@DOMAIN.TLD" -o imapc_password="PW" -o imapc_host="localhost" sync -R -1 -u local@DOMAIN.TLD imapc:

Hope you can replicate this, too, and finally fix the issue.

-- Best regards, Sven Strickroth PGP key id F5A9D4C4 @ any key-server