To be very clear: Microsoft will provide support for Microsoft Exchange issues if you run Exchange on a VERITAS Storage Foundation platform. However, Microsoft will only troubleshoot and attempt to resolve Exchange-specific issues up to the point that the source of the problem can be reasonably attributed to an issue or incompatibility with VERITAS software. This same principle also applies to other third party products.
The same is true, of course, from replication products from all other vendors, too: Microsoft supports Exchange, not random replication (or AV, or anti-spam, or …) tools. PSS won’t tell you to jump in a lake when you call them with a problem, but if the problem turns out to be caused by the third party product, MS will direct you to them for troubleshooting.