Can't send e-mail from Task Scheduler - any idea why?

Hello,

I have just discovered task scheduler (TS), and would really like to use
it to send e-mails. I tried setting up a task under Windows Calendar,
but the task always fails. The error is...

Task Scheduler failed to complete task
"\Microsoft\Windows\WindowsCalendar\test" , instance
"{fa9aeb7d-1430-4464-a18c-fade6711b561}" , action "test" . Additional
Data: Error Value: 2147746321.

Looking at the log of the e-mail server, it looks like it did try to
connect to the server, but never got anywhere. Here is one such
conversation...

"SMTPD" 2520 38020 "2009-07-01 14:57:34.666" "10.0.0.20" "SENT: 220 mail.pixata.com ESMTP"
"SMTPD" 2520 38020 "2009-07-01 14:57:34.666" "10.0.0.20" "RECEIVED: EHLO Ermintrude"
"SMTPD" 2520 38020 "2009-07-01 14:57:34.666" "10.0.0.20" "SENT: 250-hmailserver[nl]250-SIZE[nl]250 AUTH LOGIN"
"SMTPD" 2520 38020 "2009-07-01 14:57:34.666" "10.0.0.20" "RECEIVED: AUTH LOGIN"
"SMTPD" 2520 38020 "2009-07-01 14:57:34.666" "10.0.0.20" "SENT: 334 VXNlcm5hbWU6"

Ermintrude is the name of the Vista machine I'm running TS on, which has
an IP address of 10.0.0.20, and mail.pixata.com resolves to the name of
the machine on my local network that's running the mail server
(hMailserver).

I have set the mail server to allow unauthenticated messages from my
machine, but that hasn't helped.

I also tried using my ISP's SMTP server instead of my own, and got the
same error message in TS.

Anyone any idea how I can get this resolved? TS looks like a great tool,
but this problem has stumped me.

--
Alan Silver
(anything added below this line is nothing to do with me)