"Mailbox is read-only.", but it isn't

[cl@xxxxxxxx]

I have an odd problem with a mail spool file.

The mail spool file is /var/mail/cgreen, permissions are:-

    -rw-rw----    1 cgreen   mail       835067 Jan 24 09:38 /var/mail/cgreen

I can edit the file directly using (for example) vi and can delete a
message and write the file this way.

However when I try and delete (or move) a message using mutt it just
says "Mailbox is read-only.", what's the problem?

-- 
Chris Green (chris@xxxxxxxxxxxx)