We have several users who when they send an attachment with their email, the attachment is being changed to a winmail.dat file and cannot be opened by the recipient. I have looked on the Microsoft site and have found that this file is usually added to an email when the recipients email system cannot interpret TNEF (Outlook Rich Text Format). However, my problem is that this file is not being attached in addition to the original attachement, but is actually replacing the original attachment. I have tried switching off RTF and using plain text instead. Has anyone got any other ideas? Thanks