E-mail is used for an administration of your user account and for an alarm messages of your devices.
Phone e-mail is the special type of e-mail, which can be sent on your phone as SMS. This e-mail is used as free SMS for the alarm messages.
The alarm messages can be sent direct (and faster) on your Phone by full SMS. By this way you can get more information about your devices.
E-mail, Phone e-mail and Phone are default parametres of your devices, but everyone can be changed independently for any devices.