>>> Only other Outlook clients do anything with it.<<< ***
Though annoying, the .dat file serves one useful purpose if one knows/understands what happened, and could then #suggest (ie, “extend an invitation”) to the emailer to post the file thru the web or another email client.
If it could be stripped then I #suggest a warning be added to notify that there “should have been” a real attachment with the message.
*** #aside: I’m not sure that’s accurate. If the original email is “misconfigured” as an RTF, my Outlook client still receives a useless .dat file. My recollection is that I would receive the intended file on my AOL app, but garbage thru my Outlook PC. As least that’s my recollection?