Per your request, here are the lists:
Email Gateways:
There is no support list since the product is capable of integrating with any MTA that knows to route the mail to an outside source and accept connections from that sources. For example:
Symantec Brightmail, Ironport and more.
Web Gateways:
The Web Gateway has to support the ICAP protocol (ISA is an exception). here is the list:
Squid, ISA with ISAPI plugin, Bluecoat, Webwasher
Kind regards,
Naor Penso