I'm triying your widget and it is working perfectly, the common inbox show the messages from all my current gmail emails accounts (are 3).
Anyway, i'm facing a small problem: when i click in the widget board to open a message from one of these accounts (is a custom gmail domain, not @gmail.com) the gmail app get open but it show a message telling me that it is not a valid gmail account regardeless it is configured and working perfectly in that main gmail program and showed in your wondeful widget.
Clicking in messages received in any other acount works right and the widget send me to gmail app opening the right message.
Do you know where could be the problem? Could be that you have hardcoded the gmail.com suffix?
Customer support service by UserEcho