I ran into an odd issue with sieve rules. They make a bogus directory show up in the mail apps. The workaround is to put an override into config/dovecot.cf
plugin {
sieve = /var/mail/sieve/%d/%n/.dovecot.sieve
sieve_dir = /var/mail/sieve/%d/%n/sieve
}
I actually like this fix better than the one that’s working its way through mailserver.
Here’s a reference to the issue: https://github.com/tomav/docker-mailserver/issues/508