We have an external secondary MX which tries to deliver mail to the primary MX (exchange 2013) with a sliding scale schedule, which goes from 5 minutes all the way to a week. It happened that our server was down for more than 24 hours during the weekend and the messages held by the secondary MX waited there for several days before being delivered, although the server was back up.
As the secondary MX supports the ETRN command to trigger a delivery attempt, is there a way to issue that command upon Exchange's startup (or any other time)?