dsync having problems with @-sign in mailbox names

[Sami Ketola]

> 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