The last few days I have been dealing with an error where the "permissions on /var/spool/qpsmtpd are not 700"
There is nothing to deal with. The permissions on /var/spool/qpsmtpd are not 700, nor should they be. If you change them to 0700, then virus scanning will break.
How have you "been dealing with" this "error"?
Easy enough to fix, but can't figure what has caused this - started on 7.2 and continued after an upgrade to 7.3 yesterday.
When rebooted the error recurs and mail delivery obviously stops. Any suggestions on the sudden cause of this?
As you are told every time you post here:
Don't report problems here - Please report bugs and potential bugs in the bug tracker
Expect things to "just work". If they don't, then please report details to the bug tracker.