Well, this job is interesting, and as i can see simpler that it seams.I would use asp or aspx tecnology, but it can be done also in php or java. The job can be splited in 2 lines:
1. the process that catch the incoming mails and starts the outgoing mails
2. the process that parse the requested html page and builds the formated email body with the page data.
Well, i think i would really like to do this job, and i confident that i can do a very good job for you.