A piece of software produced by Lotus that allows for synchronization of a PDA with their Notes groupware. It allows for, among other things, synchronization of mail, calendar entries, and contact lists.

One unfortunate side effect is that installation of EasySync has a tendency to obliterate your existing addressbook, and nothing short of a complete restoration of your PDA's memory will bring it back. (And if someone knows of an easier way, please, for the love of god, /msg me.)