Database mail issue - any ideas?

We recently installed 2005 and have been playing with it. I seem to be
having a problem with Database Mail as it relates to job notifications,
and wanted to see if anyone knew what I was doing wrong or how to fix
this issue.
We've enabled Database Mail using the SAC tool. I've set up a mail
profile & account successfully and sent successful test messages. I
followed the instructions here (
http://msdn2.microsoft.com/en-us/library/ms186358.aspx ) on configuring
SQL Agent mail to use my Database Mail profile. But alas - no messages
ever arrive. In the SQL Agent log, I see this:
Message
[264] An attempt was made to send an email when no email session has
been established
Everything seemed rather straightforward....am I doing something wrong?
Did you run msdb.dbo.sysmail_start_sp? Try
msdb.dbo.sysmail_help_status_sp and see what the result is.
-KJ
|||The result was...
STARTED
|||You may need to define an operator.
|||I also defined an operator (myself). The operator email has the same
email address as the test message that was sent successfully, so I know
everything outside of SQL is working (SMTP relay, etc.).
|||OK - got it figured out. I just had to stop & restart the service,
which I did through SAC tool. Then I immediately received my next test
from the job.