You can take a look at this site
http://www.annoyances.org/exec/show/article08-104

"alex" wrote in message
ups.com...
They're using Outlook '03 to receive the mail. They get a message
like "Outlook blocked access to the following potentially unsafe
attachments". I'm trying to send these attachments intra office; I
know they're safe. I'm unsure if I have access to the mail server.
I didn't know if there was a work-around, other than the one I
mentioned above.