Does Roundcube have an SMTP message submission daemon for GPG

[micclay]

Does Roundcube offer a way to sign outgoing messages with a PGP key.  We've installed the Enigma plugin, which is great for emails composed within Webmail, including a passwordless option as well, but it doesn't encrypt the messages processed through SMTP. 

To put it in technical terms that I found online from Gnu Anubis:  Our Mail User Agent (MUA) doesn't modify the outgoing message before it reaches the Mail Transport Agent (MTA). For example, we wish to sign outgoing messages with our PGP key, but our MUA does not support this operation.

Is Gnu Anubis the daemon we should use with Roundcube?  I'm hoping there's a Roundcube plugin that's easy to implement, like Enigma.  And if not, what would be the best solution?

Thanks!