I am running a postfix mail relay server that handles outgoing emails from several websites that we host.
Occasionally it seems that a specific email will get stuck and postfix refuses to process any other mail until I manually delete the email from the /var/spool/postfix/active directory.
The error message in the logs is:
fatal: qmgr_message_alloc: [message_id]: remove defer [message_id]: Permission denied
I've checked the permissions on the defer and deferred directory (not sure which it's actually complaining about) and both are owned by postfix:
drwx------. 18 postfix root 4096 Jun 1 2015 defer drwx------. 18 postfix root 4096 Jun 1 2015 deferred
This has only happened two or three times in a few months, otherwise processing normally and able to defer other mails. I can't find anything particularly different with the emails that get stuck.
Can anyone shed any light on this error message?