The "S:" prefix indicates the subject of the message and is set by the title of the notification. Everbridge includes the "S:" so the entire content of the message is delivered to message recipients, and also to maintain message content consistency, as not all message delivery providers include the prefix by default.

As shown above, the contact would receive an SMS message based on the notification pictured on the right. The Title "High Wind Advisory" is the subject ("S:") of the text message, and the Body follows immediately after on a new line.

The title of a notification is a required field for notifications, but it can be removed from SMS messages.

See the following article for steps to remove the "S:" characters: Disabling SMS Subject Line from Text Messages.