if its a windows phone and software driven (it is) then it doesn't work for me either
has one master volume, and thats it...totally sucks.
also, very few tones for notifications, and no, the operating system is NOT smart enough to differentiate between COMPLETELY different applications to alert you
even though, android has been able to do this since its inception.
the more i use my windows phone, the more i fondly remember my G1's power and usability.
sad that microsoft cant even copy an idea (like bing cant ever defeat google with all the advertising ever known).
what you could do, is not sync your gmail (or only sync gmail manually) and let your work email sync however often you need it...