Here is an example of how to send a multipart email message with ColdFusion:

view plain print about
1<cfmail subject="MultiPart Email Test" type="text/html" to="you@test.com" from="someone@test.com">
2 <cfmailpart type="text/plain">
3 Plain text goes here
4 </cfmailpart>
5 <cfmailpart type="text/html">
6 HTML version goes here
7 </cfmailpart>
8</cfmail>

It's important that you put the text-only version of the message FIRST in the mailpart tag list, otherwise GMail will always display the text-only version of the email message and never display the HTML version of the message!