[dovecot] Failed to create storage

[M]

Hi,

I'm impressed so far, I tested this before trying to run it on a mail server and it worked find.
However on the mail server with the same config I get the following message when I try and authenticate, and it drops the connection.

Failed to create storage with data: mbox:/var/mail/martin

The test box is running debian unstable and the mail server is running debian stable so I had to recompile and install.
I'm failry sure that I got all the permissions right, I feel like I'm missing something obvious, can anyone advise?

The file and permissions on the mailbox look right:
-rw-rw----    1 martin   mail     14743740 Jan 10 06:29 /var/mail/martin

-- 
Thanks,
M