editdata.mso attachment

When sending an email, the recipients also receive an editdata.mso attachment. I’m not sending this attachment myself.
Where is this attachment coming from?

This issue can occur when you are using Outlook 2003 or previous and have Word set as your email editor.

The editdata.mso contains macro and OLE object related data to make certain formatting and functionality available in HTML formatted Word document. This basically is the case when using Word as your email editor; a Word document is being send out as the email body which is in HTML format.

To prevent this from happening (other than disabling Word as your email editor), make sure you have your HTML filtering options for email in Word set to Medium (default) or High;

1. Open Word.
2. Choose Tools-> Options…-> tab General
3. Click the button E-mail Options…
4. You can set the HTML filtering options on the General tab.
5. Press OK and then OK again to close the open dialogs.

Note: Outlook 2007 is not affected by this but you can of course still receive these attachments as it depends on the sender and not the receiver.