[Dovecot] invoking LDA in .forward

Hi,

We're running a Debian server with system users where the mail is by default delivered by postfix and procmail, before being served by Dovecot (mail_location = mbox:~/Mail:INBOX=/var/mail/%u) or read by local MUAs, depending on users' preferences.

For people using mostly remote MUAs, it might be interesting to use Dovecot's LDA. I read on http://wiki.dovecot.org/LDA that this is possible using .forward files, however this fails on our system with : file_lock_dotlock() failed with mbox file /var/mail/user: Permission denied (/var/mail is 2775 for root:mail as recently discussed).

Is there a possible fix ? I also read that deliver is not designed to be run setuid root, I guess this also applies to being run setgid mail...

Regards,

Jeremie