Is there a way to route mail from Appian to a mail server (Appian Cloud )

HI hope this will help
forum.appian.com/.../Sending_an_Email_Message_to_a_Process.html

Do you want to use your own email server for out going email?

Hi. Tx for the info

Yes. We want to use our own email server for outgoing mail

Appian documentation doesn't mention about if that setting is configurable for cloud environment. I suggest you take the Appian support route.