Delete old messages: Checkmark this setting to allow the phone to delete older messages in a thread when the Text message limit or Multimedia message limit is reached. Remove the checkmark to keep all of your messages.
Text message limit: Opens a dialog box to set the number of text messages to save per thread.
Multimedia message limit: Opens a dialog box to set the number of multimedia messages to save per thread.
Signature: Opens a dialog box to enter a signature to automatically send with your messages. Checkmark appears after a signature is entered.
Callback number: Opens a dialog box to view or edit the callback number sent with your messages. Checkmark appears after dialog box is closed.