SMIME conformance specs

["Piers Chivers" <piers@xxxxxxxx>]

Hi,
Are there any publicly available docs that describe the conformance
requirements for a PKIX/SMIME compliant messaging client?

I know that the SMIME RFCs detail the protocol requirements for a conforming
app but I was thinking at the level of
"A conforming client must indicate to the user when a message fails a
signature validation" or "A user must be able to encrypt and/or sign an
outgoing message".

Thanks,
Piers