I want to thank everyone for your comments. I have learned a bunch just from reading your replies. My current environment consists of a firewall, a HP/Compaq VMS server running PMDF (full-blown MTA with filtering), many multi-vendor servers (windows, UNIX, HP) and Exchange. With the soon to be migration from Exchange 5.5 to 2003, we were contemplating the use of Windows SMTP as the MTA instead of the VMS server running PMDF. With all your comments, my feeling is to put in place a Windows 2003 SMTP server, but still keep my VMS server. This adds another hop to mail and data transmissions, but I'm told that if and when we ever decided to use Windows 2003 as our primary SMTP/MTA server, it's better to put it into place now then to add it later. Our Exchange migration will happen in the next month - which is way to early for me to decide what MTA I would move to if I moved off the VMS server. However, I do want the infrastructure in place just in case. Something that PMDF gives me is the ability to work at the OS level and manipulate logs, change configurations, and generate reports. In addition, PMDF works on a queue level, so have a lot of control what is processed and what does not. I am not seeing any of this possible with Windows 2000/3, so now I understand the use of layered apps on the SMTP/MTA server. Comments still welcomed!