Is there a Python MTA (Mail transfer agent)

Just wondering if there is a Python MTA. I took a look at smtpd but they all look like forwarders without any functionality.

From stackoverflow

• Yes, Twisted includes a framework for building SMTP servers. There's a simple Twisted-based email server available here (also see here for some information about its development). At the other end of the complexity spectrum is Quotient, which is much more than a MTA.

• It's pretty new, so nothing like the maturity of Twisted's SMTP, but there's also Lamson.