[sup-talk] multiple accounts

[Brian]

What should config.yaml look like for multiple accounts? I have several
accounts that use different SMTP relays. My plan is to do stuff like
:sendmail: /usr/bin/nbsmtp -c /home/brian/.nbsmtp_brian_lorf_org
in each account, but I don't understand how to make sup use any account
other than :default:.

How do I tell sup to use a certain account when I compose a new message?