Asa 5540 version 7.0(7) in front of exchange 2003 enterprise with the latest service pack, and GFI antispam box, every morning we get the kick back "There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<ANTISPAM.mydomain.com #5.5.0 smtp;550 bosauthsmtp10: Host "our public IP": No unauthenticated relaying permitted>" when we try to send an email, the only way to fix this is to restart the firewall, once we do this everything goes back to normal without doing anything else on the server side, no changes have happened since this started a week ago, we have relay taken care of already long time ago and we are good in that aspect.
also, smtp fixup is unchecked on the firewall.
I'm the only administrator in the company, I have not made any changes for the past 6 months not even patching the exchange server. and everything was working fine until 4-5 days ago.