[Evolution] Account Not Enabled?

["R. A. Bilonick" <bilonickra upmc edu>]

I'm trying to send an e-mail using Evolution (2.12.3) on a Fedora 8
laptop using an account that has worked before. Now all of a sudden I
get the message:

This message cannot be sent because the account you chose to send with
is not enabled

I've checked preferences and the account is enabled - I receive e-mail
and it is (and was) set up to receive and send e-mail.

How can I fix this?

Rick B.