Whenever I send an attachment through Outlook, the recipient receives the email without the attachment although they sometimes say that it got renamed to winmail.dat.

It happens to all attachments regardless of who I send it to and the format of the file (e.g. PDF, Word, jpg, etc). If I send the same attachment through web mail or from another computer, the attachment remains intact and is received in the email.

I’ve tried turning off my anti-virus program but that’s not made any difference, so I’m assuming the issue must be within Outlook itself.