Delivery to shared folder

I have an error with delivery of emails to a shared folder in 10.4. This was noticed after the 10.4.4 combo update, but may not be related.

My first though was the update may have overwritten some config. Postfix main.cf still has the recipient_delimiter = +. Checked that anyone has post permissions to that folder. I can manually drop stuff into the folder and it is okay.

Depending on the imapd.conf I get two results. First is the message queues in postfix but gets a “temporary error”. Second when I add a “postuser” line to the imapd.conf the messages bounce immediately with an “unknown user in local recipient table”.

All other mail is deliverd ok. Is there something I’m missing here?

Thanks

Sean