[nulbyte]

Not for email specifically, but there is a flag for encrypted communications and another for signing.

https://datatracker.ietf.org/doc/html/rfc4880#section-5.2.3....

I believe separate keys for encryption and signing is the default in most implementations.

[akerl_]

Sure, but there are things for encryption other than email. Publishing an encryption key does not imply that emails sent to me should be encrypted to that key.