Sorry, got it wrong, OSA-SYNC will only run with outlook, so you will not be able to use it natively on linux, sorry.
However, you might want to give crossover office a try. They have a trial version, so go for it! I don't want to start a holy war, but crossover office is a windows emulator, which runs pretty fast on recent systems, and allows you to run ms office and other windows software on linux.
Just a thought, I do not know how the ftp sync works, maybe that could be done natively, but I would need more info on how they sync, if it is a pst file, then we are out of luck, as pst files are proprietary and linux programs don't like them and prefer the standard mbox files - which work with almost "any" email client ...