smtp credential, multiple smtp, posting styles and smtpmail

[Richard Riley <rileyrg@googlemail.com>]

Does someone have a way of extracting/setting the correct credentials
for smtp posting based on the contents of .authinfo.gpg when using
gnus-posting-styles?

The problem with msmtp is that the data is in cleartext.

The issue with smtpmail-auth-credentials is that I dont think it can easily be used
with the "logical" machine name in the authinfo.gpg e.g

  (add-to-list 'gnus-secondary-select-methods '(nnimap "riley"
                                    (nnimap-address "imap.gmail.com")
                                    (nnimap-server-port 993)
                                    (nnimap-stream ssl)))

Here the authinfo "machine" is "riley". 

I'm guessing the best and easiest way is to put my gnus-posting-styles all in
a gpg file and hardcode the smtp server and id/password in them. Anyone
out there already done this? It certainly seems the easiest if
possible. I just need to try and figure out which gnus variables are
used.

Another solution, that might even exist, would be for a server select
method to have the associated outgoing smtp server name as a parameter
and assume the same access credentials as when reading mail on that
server. Again, can I already do this?

Ideally I'm trying to avoid juggling which smtp server based on using
"from" hacks from around the web and just set access data directly using
the gnus posting style.

Googling around leaves me a tad jaded - so many options and so complex
at times ;)