Return delivery history MTA option

Notification message MTA options:  (0 or 1)
The  MTA option   controls whether or not a history of delivery attempts is  included in returned messages. The delivery history provides some indication of how many delivery attempts were made and in some cases  indicates the reason the delivery attempts failed. A value of 1 enables the inclusion of this information and is the default. A value of 0 disables return of delivery history information. The   MTA  option controls how much history information is actually returned.

See also:
 * Debug MTA options
 * history_to_return MTA Option
 * Notification message format