I'm having an odd problem with outgoing email in Outlook 2003.

I just got a new laptop w/XP Pro and loaded the MS Office Standard Suite w/SP1. I also downloaded and installed Office SP3.

I set up Outlook email w/all my POP3 settings and tested the settings in Outlook -- all fine.

Incoming email is no problem. However for some outgoing emails, I get an immediate (and I mean instantaneous) bounce-back message that looks like the following:

Your message did not reach some or all of the intended recipients.

Subject: Test
Sent: 2/5/2010 12:13 PM

The following recipient(s) could not be reached:

on 2/5/2010 12:13 PM
None of your e-mail accounts could send to this recipient.

The problem seems to be specific to certain email addresses. Some addresses I send to are fine; others get that instant bounce back. And there seems to be no domain patterns. For example, some gmail addresses work, others don't.

to check to make sure it's not my ISP or settings, I set up Outlook Express w/the same settings and all emails went out flawlessly -- no bounce back issue.

What's curious is how quickly the emails bounce back. It's not like it's traveling to the recipient, and being processed, and then returned. It's like it's being immediately rejected.

I've uninstalled and re-installed Outlook 2003 and SP3 to no avail. I also did a system restore to an earlier point to see if some software I loaded might be causing a conflict, but the problem persists. I also disbaled my anti-virus software...problem still persists. Anyone have any idea what the problem could be?