I'd suggest asking in a newsgroup related to Outlook.
Personally, though, I zip the files: Access files usually zip very nicely.
If that isn't sufficient, try changing the file extension, and tell the
recipient to change it back.
there are "add-ins" for outlook that allow you to control what is allowed.
most make you save the attachment first then open it though but at least it
will let the email come through. i don't have the name of the one i use but
do a google search and you will come up with a few. once installed, it adds
a tab to the options screen and there you can configure it to allow various
extensions. you would not believe how many microsoft thinks should not be
allowed.