With one of my email accounts I've been unable to send mail using Gnus
(in GNU Emacs 23.0.60.5 (i686-pc-linux-gnu, GTK+ Version 2.12.0) of
2008-02-14 on escher).  I use this setup (anonymized):

  (setq message-send-mail-function 'smtpmail-send-it
	smtpmail-default-smtp-server "mail.myprovider.com"
	smtpmail-smtp-service 465
	user-mail-address "Stephen.Berman@myprovider.com"
	smtpmail-auth-credentials
	'(("mail.myprovider.com" 465 "myusername" "mypassword")))

I type `M-x message-mail', type the message and send it, and Emacs locks
up for 20 minutes, then beeps and shows the message
"smtpmail-send-command: Process SMTP not running".  The buffer *trace of
SMTP session to mail.myprovider.com* shows this: