The module is called WebMailFX. Last stable version is 0.82_frz (which will soon become 0.84); last development version is 0.85.
We advise users to use stable one in their production sites: though they lack some features and some are not working, they are enough safe to use.
You'll find more infos on the following sites:
http://lnx.trashnight.org/modules/mydownloads/viewcat.php?cid=3
http://dev.xoops.org/modules/xfmod/project/?group_id=1132
Bye,
ft