Now here is a real catch-22, perpetrated by our good friends, the Microsoft Outlook development team.
As a security move, Microsoft changed Outlook sometime back to not allow recipients of an attached MS Access file (something.mdb) to even see the file, let alone save it or open it. If you get one of these files in Outlook, it's there, taking up space, but it might as well be in Timbuktu for all the good it does you.
So what happens when you try to open that email in another, smarter email reader? All you get is a lone "winmail.dat" file -- that Microsoft proprietary format which they used for "rich format" emails. Completely unusable.
In other words, don't ever use Outlook to email an Access MDB file -- it just doesn't work. Obviously someone wasn't thinking when they made this change... or they just didn't care. Take your pick.