Maybe this would help: MSKB #Q223876 OL2000: Selecting or Changing Your Message Format.
You can also try to set the BodyFormat Property to Plain text

.BodyFormat = olFormatPlain

>Hi
>
>I am in the middle of trying to send Emails by clicking a button from a text file. I have managed to save data needed to a text file using visual foxpro, this is used by microsoft outlook (using VBA) which opens the text file and creates several emails depending on the information in this file, for example
>
>SUBJECT=One, This id for the subject of the email
>ATTACHMENT=c:\one.doc
>BODY=This is for the body of the email
>***** && Indicating end of first email
>
>SUBJECT=Two, This id for the subject of the email
>ATTACHMENT=c:\two.doc
>BODY=This is for the body of the email
>***** && indicating end of second email
>
>VBA would loop through this text file creating two emails and adding the specified attachment.
>
>This works, however, the problem is I need the format to be PLAIN TEXT, but whatever I do it creates it using RICH TEXT. Ive tried manipulating it using the format option on the outlook toolbar, rules but I can't seem to get it, could anyone have any ideas which would help me?
>
>Thanks
>Nelly