dsync having problems with @-sign in mailbox names

[Philip Iezzi]

> On 28 Sep 2019, at 11:28, Sami Ketola via dovecot <dovecot at dovecot.org> wrote:
> 
> 
> 
>> On 28 Sep 2019, at 12.21, Philip Iezzi via dovecot <dovecot at dovecot.org> wrote:
>> 
>> Hi there
>> 
>> We are running Cyrus-to-Dovecot migrations using dsync on destination Dovecot server (Debian Stretch / latest Dovecot 2.3.7.2 from community repo) like this:
>> 
>> $ doveadm -o mail_fsync=never backup -R -u <username> imapc:
>> 
>> For imapc configuration to connect to remote Cyrus server, see below [1].
>> While this works great for hundreds of mailaccounts, dsync fails with the following error on accounts with @-sign in mailbox names:
>> 
>> dsync(<username>): Error: Failed to access mailbox INBOX/entrance/admin at example: Invalid mailbox name
>> 
>> I can confirm, Dovecot supports @-sign in mailbox names and no client (tested with Thunderbird, Apple Mail, Roundcube webmail) has issue with this character.
>> Also Cyrus was always supporting this. So I guess this is an issue with dsync. Can we somehow tune charset (UTF-8 ?) in imapc configuration?
>> 
> 
> Hi,
> 
> can you please try to record imapc rawlogs for such an session? I would like to see what kind of mUTF7 name string Cyrus sends for these folders that have special characters.
> We have been able to work around some of the broken mUTF7 implementations with some BROKENCHAR magic.
> 
> Sami

Hi Sami,

Thanks for your support. I have tried the following...
Added this to conf.d/20-imap.conf:

protocol imap {
  rawlog_dir = /tmp/rawlog/%u
}

Then restarted Dovecot, and re-run the following dsync migration:

$ doveadm -o mail_fsync=never backup -R -u <username> imapc:
dsync(<username>): Info: imapc(imap.example.com:993): Connected to x.x.x.x:993 (local y.y.y.y:45726)
dsync(<username>): Error: Failed to access mailbox INBOX/entrance/admin at example: Invalid mailbox name

Then checked /tmp/rawlog, which is still empty. According to https://wiki.dovecot.org/Debugging/Rawlog, setting `rawlog_dir` should be the only thing needed, right? What did I do wrong?
I am glad to provide you the raw logs as soon as I can generate them.

Thanks,
Philip