you go to the "System" tab, then to "Setup", then to the "QlikViewServer" node, then to the "Alerts" tab and configure it there.
Get the details of your Xchange server from your IT_guys.
Alternatively, go to "System" tab, to "Setup" and there should be a "email server" node, too.
That is for alerts ONLY in case that a reload_task fails. Any other alerts (rgd. any specific circumstances in the data) you will have to set up in the app itself after configuring email details (the same as here) in the user_settings.