Gnus Agent and From address of email

[Phillip Lord]

I change the "from" address for my email a lot. One problem is that when
using gnus agent, this does not appear to work -- that is the from field
is set to whatever user-mail-address is configured to at the time that
the queue is sent, NOT at the time that the email was sent (to the
queue). This makes offline email less useful as I can only send email
messages with one from field at a time.

Or am I doing something wrong?

I am sending email with msmtp using sendmail-sent-it.

Phil