AOL Mail & attachments from Outlook

I have to sent attachments to several AOL users. When I send them from Outlook they endup as "WINMAIL.DAT" files. If I send them from Outlook Express, thay arrive just fine. Has anyone had this problem, and if so how did you fix it. I am tired of having to send each message from two different email programs. No, having the users change over to a real ISP is not an option. Already suggested that to the users, was met with hostility and death threats ;).