outlook cannot connect to outgoing smtp

[naplespat...@discussions.microsoft.com]

I have outlook 2003. When I send email I get the following message:
error (0X80042109) Outllok is unable to conect with outgoing (smtp) email
server.

The messages I try to send sit in my outbox.
I have done the following:
Moved the computer to another home. I am able to send messages via outlook
from there (also on comcast)

From this computer in this home i am able to send mail via comcast.net, aol,
or from the Multiple listing service (I am a realtor) - just not from
outlook. I have tried switching the port from 25 to 587, when I do that the
test message works and is sent, but the outgoing mail still won't go. I have
spoken with someone at Comcast, they really were no help except to suggest
changing the port. That did not work. after reading a lot, I think it could
be a stuck "read receipt"???? I don't know.