well there might be a way to do it, but I haven't tried it myself. The basic idea is to add a header to the email, and format the email with boundaries. the message will look like:
--boundary___1
Content-Type: text/plain
Plain Text Message Here
--boundary___1
Content-Type: text/html
HTML Message Here
--boundary___1--
then you want to add the email header :
Mime-Version: 1.0
content-type: mutli-part/alternative; boundary="boundary__1"
of course your email client won't let you mess with the header, but many web programming language can do it, for example php has a mail function with which you can craft a totally customized email. You might want to ask around people and see if any technician in your company knows how to program php, and tell him/her the basic idea and you might get some help.