I have been looking around for an open source java web mail implementation, there aren't many around and what I located seemed like serious bloatware.
To create a basic IMAP mail client in java takes only a few hundred lines of code. If you refine it and secure it it may run upto a couple of thousand lines, such a system shouldn't really be more than 1MB in download size (even with the graphics for the websites).
Apperently many developers seem to think bigger is better, they are plain old embarrased by their small size (small size of their downloads that is). As a result they seem to have added every kind of open source library they can find as part of their download bundle. Plain old rediculous i have more upto date versions on my hard disk, and have to do an extra step to update them.
Of course all this applies to almost every kind of software not just mail clients. At Rad Inks we are at the other extreme we try to keep our downloads as small as possible. Small is beautifull.