Encryption Server to decide PGP or TLS (mail) encryption

Hi all.

I've just been asked if the Encryption Server is able to "decide" if PGP or TLS encryption should be applied. Scenario is that normally all mails are PGP encrypted, however it is required for a few external parties not to apply PGP encryption but TLS encryption (gateway2gateway). 

AFAIK, the Encryption Server is not able to "moderate" or make this decision, it has to be an external agent, let's say the mail server just before sending the mail to the Encryption Server OR a MTA which receives, PGP encrypted or not (depending on the mail policies), the mail coming from the Encryption Server.

Anyone  experience with such scenario?

Thanks.