These are compatibility issues with Postfix caused by the smtp fixup or CISCO SMTP/ESMTP inspection of old CISCO ASA version. CISCO SMTP/ESMTP inspection is very strict with RFC compliance and can cause issues when you use Exchange 2007 servers, which may not be very strict with RFC compliance.
To resolve the issue:
- Download Cisco ASA 5500 Series Release Notes Version 8.0(4).
- Disable the SMTP and ESMTP inspection in ASA by running the following commands:
- policy-map global_policy
- class INSPECTION_DEFAULT
- no inspect esmtp
- no inspect smtp
To ASA firewall administrators, you may disable SMTP/ESMTP inspection in CISCO ASA because it is very stable and works well.