No specific reason why not, have you tried building them in the sdk ? (probably the phrozen one)
I don't know what the build dependencies are like for Exim so you may have a bit of fun satisfying them. Unless someone has it kicking around I am not aware of a ready built set of binaries. Also you would probably need to mount some more storage somewhere to deal with the mail queue. Dunno what sort of mail volume it will handle given the limited memory and cpu resources but if you can get exim to build in the sdk then it could be made to work.
