Filename of file to be used as alternate text to display in email programs that do not support/display HTML messages.
Other Parameters Required:
The filename is that of a plain text message file (which, of course, may contain newlines, thus you can use this to specify more substantial plain text alternative message bodies).
Example (cut-and-paste right into your batch file):
NetMailBot -altbodyfile "C:\My Documents\plain_text_newsletter.txt" -to email@example.com -from firstname.lastname@example.org -server mail.domain.com -subject "test"
If you were to use them both at the same time, -altbody and -altbodyfile would behave additively.