Outlook 2003 is rejecting 1 email address

Factual Questions
1

I am having problems sending emails to just 1 address. I have tried sending, letting Outlook pull the address from my address book. I have tried typing the address in directly. I have cut and pasted the address from other emails.

There are 2 ways I can get an email to go:

  1. I can reply to an email that this person sends me first.

  2. If I put another email address, outside my company, on the To: line, and this address on the CC: line, I can get them to go.
    a) Putting this address on both the To: and the CC: lines doesn’t work
    b) Putting my company internal address on the To: line and this address on the CC: line doesn’t work.

I have only had this problem with this one address, and only MS Office 2003. The recipient isn’t have problems with anyone else’s email.

The error messages read: The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.

Have anyone else seen this, or have any suggestions?

2

My first instinct is to guess the problem is an overaggressive spam filter. Not really enough information to come to a conclusion yet though. Where is the error message coming from? Is it from your outgoing mail server or the mail server on the receiving end?

3

I was wondering about the filter thing, but would a filter let through an email that was a reply, but not one that was an original? Or let through an email to another employee in the same office?

The “From” address on the error message is only “System Administrator”, so I’ve assumed that it’s from my outgoing server. Unfortunately, because of all the addresses in it, I don’t want to post the “Internet headers:” info.