I'm using YouTrack 5.1 build 8447.
All notifications do not come from the right e-mail address.
I initially configured it with my own address during test phase and later changed to a more appropriate one.
I re-checked configuration page: everything is correct, but all notifications, from any user, I receive are marked with the full name of the user and the old e-mail address.
The only time the YouTrack e-mail comes from the right address (and name too) is when i use the dedicated test command.