You can disbale it in Acymailing-Configuration->Licence by disabling the Automatic send process. When you do this your automatic sending won't work anymore.
On the other hand if someone triggers that url your Acymailing will get triggered, but if there's notheing to be send nothing will be send. Triggering that url is pretty harmless. Unless you get a massive amount of times it egts triggered in a short period of time.
Regasrding your off-topic question, you can click on your name in the top right corner and adjust your settings for notifications and e-mails.