To add an external user click the Edit button on the External Users window.
Make the changes you want and then click OK.
Username
This field is mandatory.
Email
Enter an email address if you want the external user to receive their messages by email.
Mobile/Cell Number
Enter a mobile/cell phone number if you want the external user to receive their messages by SMS (note that MessageSender requires an SMS Gateway account for this feature).
Pushover Device
Enter a Pushover device name if you want the external user to receive their messages by Pushover (note that MessageSender requires a Pushover account for this feature).