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Postfix Documentation
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Testing the Postfix fast ETRN service

By default, "fast ETRN" service is enabled for all domains that match $ relay_domains. If you run Postfix with "fast ETRN" service for the very first time, you need to run "sendmail -q" once in order to populate the per-site deferred mail logfiles. If you omit this step, no harm is done. The logfiles will eventually become populated as Postfix routinely attempts to deliver delayed mail, but that will take a couple hours. After the "sendmail -q" command has completed all delivery attempts (this can take a while), you're ready to test the "fast ETRN" service.

To test the "fast ETRN" service, telnet to the Postfix SMTP server from a client that is allowed to execute ETRN commands (by default, that's every client), and type the commands shown in boldface:

220 my.server.tld ESMTP Postfix
helo my.client.tld
250 Ok
etrn some.customer.domain
250 Queuing started

where "some.customer.domain" is the name of a domain that has a non-empty logfile somewhere under $ queue_directory/flush.

In the maillog file, you should immediately see a couple of logfile records, as evidence that the queue manager has opened queue files:

Oct  2 10:51:19 
myhostname postfix/qmgr[51999]: 682E8440A4:
    from=<whatever>, size=12345, nrcpt=1 (queue active)
Oct  2 10:51:19 
myhostname postfix/qmgr[51999]: 02249440B7:
    from=<whatever>, size=4711, nrcpt=1 (queue active)

What happens next depends on whether the destination is reachable. If it's not reachable, the mail queue IDs will be added back to the some.customer.domain logfile under $ queue_directory/flush.

Repeat the exercise with some other destination that your server is willing to relay to (any domain listed in $ relay_domains), but that has no mail queued. The text in bold face stands for the commands that you type:

220 my.server.tld ESMTP Postfix
helo my.client.tld
250 Ok
etrn some.other.customer.domain
250 Queuing started

This time, the "ETRN"" command should trigger NO mail deliveries at all. If this triggers delivery of all mail, then you used the wrong domain name, or "fast ETRN" service is turned off.

Finally, repeat the exercise with a destination that your mail server is not willing to relay to. It does not matter if your server has mail queued for that destination.

220 my.server.tld ESMTP Postfix
helo my.client.tld
250 Ok
etrn not.a.customer.domain
459 <not.a.customer.domain>: service unavailable

In this case, Postfix should reject the request as shown above.

Postfix Documentation
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