It depends on the sending method you’re using. If you use our free version, you will use the “manual” sending method so if you close the window then the send process will stop. If you use our commercial version and use the “automatic only” send process, then AcyMailing will add your e-mails in the queue and take care of the send process using a cron task. So you can log out, turn off your computer and do something else.