The following is an example SMTP session that shows how an SMTP
client requests the ETRN service. Client commands are shown in bold
220 my.server.tld ESMTP Postfix
250 Queuing started
As mentioned in the introduction, the mail is delivered by
connecting to the customer's SMTP server; it is not sent over
the connection that was used to send the ETRN command.
The Postfix operator can request delivery for a specific customer
by using the command "sendmail -qRdestination" and, with
Postfix version 1.1 and later, "postqueue -sdestination".