Turn off bounce#
Globally#
$ defaults write -g NSScrollViewRubberbanding -int 0
App Specific#
$ defaults write com.apple.mail NSScrollViewRubberbanding -int 0
Restore bounce#
Globally#
$ defaults delete -g NSScrollViewRubberbanding
App Specific#
$ defaults delete com.apple.mail NSScrollViewRubberbanding
Mac