One thing we can rely on a Office-Watch.com is the regular flow of emails asking about Winmail.dat attachments to emails. What they are and what to do about them.
Winmail.dat is part of Microsoft’s own Rich Text Format for emails. RTF has been mostly superseded by the more open HTML based email format but RTF is still there and pops up, unwanted, from time to time.
Winmail.dat are a nuisance but Microsoft has never said they would ‘fix’ the problem. Redmond considers winmail.dat necessary for emails within the Exchange Server environment.
That said, we’ve done some articles on Winmail.dat.
What to do .. for Winmail.dat Senders
note that the standard advice for Senders is NOT complete. It ignores lingering ‘RTF’ settings for contacts. Our page How to stop sending winmail.dat covers all the places to have to check.