Look at acs-tcl/tcl/html-email-procs.tcl, which contains the handy proc build_mime_message, and bulk-mail/tcl/bulk-mail-procs.tcl for an example of how to use it. You will have to make one edit to the first file - someone renamed base64.tcl to base64-procs.tcl but didn't change the reference to it. I will be committing a fix for that soon, along with some other stuff, but the copy you have will be wrong.
