Can't move/delete folder "Renaming not supported across conflicting directory permissions"

[Aki Tuomi]

On 24.2.2020 10.04, Johannes Rohr wrote:
> Dear all, 
>
> several users have reported that they were unable to move/delete
> folders using Thunderbird and they got the message "Renaming not
> supported across conflicting directory permissions". When I google for
> this message, I see hints like "your mail may not be all on the same
> volume", but here this is definitely not the case. All mail is in
> /var/mail/virtual and owned by mail:mail
>
> Curiously, when I tried the same operation in Roundcube, there was no
> error reported, so something about the combination of Thunderbird and
> Dovecot seems to be causing the error. 
>
> Does anyone have advise on how I should go about tracking down the
> cause of the error?
>
> Thanks a lot in advance!
>
> Johannes 
>

Perhaps mail logs would reveal more?

Aki