Have never used or set-up MS Exchange - but have many Lotus Notes Domino applications running with IIS (from 5 to 7). The trick is to change the default http address (Notes in my case, MS Exhange in yours) from the default (80) to some other not in use port (like 84), and https 443 to say 446
Your IIS web service will run without any problems, and if MS has web admin/email (like Notes) then users can access it by typing http://YourDomain.com:84 or https://YourDomain.com:446