Block stationary in emails for all outgoing emails in a corporate environment

Recently at an IT staff meeting, my boss told me that one of our VPs was quite annoyed with all the different stationary being sent out via email from our internal staff. A good example is Jane from accounting likes to use a pink background while Bill from HR likes to use a green and black mash up for all outgoing emails (or flowers, and balloons may be on an email). The VP was quite annoyed with this and deems it unprofessional when sending emails out as a representative of our organization. I've been tasked with blocking stationary from going out with emails. Now for starters, I've never tried this before and knowing Exchange, I very much doubt I'm going to be able to find a native solution for this, but rather seek out a third party solution. I'm running on a Windows 2003 server environment with Exchange 2003. Now because I've never tried to do this before, I'm speculating that I might be able to block HTML content from the server level, or block stationary via group policy to the Outlook client. The problem with both of those options are that users may want to pass off legitimate HTML content at times, and group policy wouldn't work as more than half of my end users are in branch offices using RPC over HTTP. So with that said, do you guys have any solutions? Whether they be native or third party do you know of a solution for me to reach my objective? Also as more of a cherry on top item, I wouldn't mind including a little company logo on all emails, I already have a disclaimer in place using GFI, but that's obviously just text.