Storace Exec 5.3 - File Content Signatures

Hi guys, running the now unsupported Storage Exec 5.2 HF 24. I'm trying to ensure that file content checking blocks e-mail files but there are no signatures in the registry for .msg files etc. Is it possible to create them? I assume they are some sort of reg expression check against the file hearder or hash?

PS: I'm looking to move away form this product obviously!