RSASSA-PSS p1v2.1 (rfc 4056) signing
Is p#1v2.1 still not supported by outlook/microsoft or am I just crazy?

PSS seems still not introduced to Microsoft, please see here. It's a long discussion, but in the end it seems that you cannot select PSS as a signature scheme when sending, I presume that also means that PSS signatures are not accepted.
RSA-OAEP based encryption is generally supported earlier than PSS. There are padding oracle attacks against the PKCS#1 v1.5 encryption scheme. The PKCS#1 v1.5 signature scheme is still considered secure, so there is much less need for upgrading it.