cannot send to a specific address?

whenever I try to send an email to one particular address, it gets bounced immediately from "system administrator" with the error message

The following recipient(s) could not be reached:

' on 6/7/2004 7:55 AM
None of your e-mail accounts could send to this recipient.

i know it is not making it out of the internet, the message has no headers whatsoever and if i reply, it tries to send it to system administrator, no email address. Also, the message has a strange icon next to it in my inbox, not a normal envelope, but a circle with a red arrow on it pointing left with a bunch of squiggles to the right of the circle. i can post a picture if you guys want to see...

there is also an attachment to the message that cannot be opened....the paperclip icon is there but it doesnt look like there actually is an attachment. what would be causing this email to not even be tried to be sent out? i've test the recipient's email address using my web based email and it works fine, but not through outlook

this is the only email address that this has ever happened with

thanks