Dsync deleting mailboxes due to duplicate UIDs

[Sami Ketola]

> On 10 Sep 2018, at 0.05, Andreas Thienemann <andreas at thienemann.net> wrote:
> 
> Following the robustness principle it feels to me that it would make sense for dsync to disregard a duplicate header from a remote server and only use the first occurence.
> 
> Would that be a good approach to the problem? Now that I understand the problem I am having, I can just workaround it but it seems to me that dsync should handle this case better.
> 

Currently dovecot does rely on remote to send valid RFC-compliant headers. But you are not alone, we have seen similar problems with mixed header fields on some legacy servers on the migrations we have performed.

I have found dsync_hashed_headers setting as a good workaround for migrating mails from broken imap servers. As per RFC Message-ID should be unique and we have safely used setting dsync_hashed_headers=Message-ID to migrate the problematic users away from the broken servers.

Sami