Win 7 Prof
java version "1.6.0_17"
Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)
Since V7.2.5 "send test mail" always failed (at least with my gmail account).
It is difficult to know the reason because the error message is so complicated (see log in attachment).