Outlook

I am using Outlook for my email, while the standard at my company is Netscape. I have been experiencing problems with attachments that are losing their file association when sent to a person running Netscape Communicator. It turns up on their end asa *.DAT file that they cannot open, even though they have the software. Happens on all software suites, not just Microsoft Office…Anybody run across this and whats the fix. Email me off of the list if possible