Unknown .dat files attach to my outgoing email, how do I stop it?

[Guest]

When I write a new email message in Outlook the recipients report back that
there are unknown and unexplained .dat files attached to the email, files I
know nothing about and that they cannot open. This does not happen when I
compose my mail in ms-word and send it out of outlook. It only happens when
I compse the email in Outlook. I have run anti-virus and found nothing.
What is this and how can i stop it.

 

[neo [mvp outlook]]

If the file is named winmail.dat, try changing your message format to plain
text or html and consider disabling Word as your e-mail editor.