You notice the message: enabling pix workagorunds regularly in your logfiles
This message is just information and means that your mailserver is communicating with another mailserver behind a cisco pix firewall and the firewall has its fixup smtp protocol enabled. Your mailserver is not talking directly with their mailserver but with the firewall who relays the smtp protocol to their email relay. This fixup smtp protocol had buggy code and postfix can recognize this and activate a workaround. It does NOT indicate a problem.
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience, including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform.