I have a account on our mail server that attempted to send email to a user on a mail server and received a NDR for the account not exisiting. when i looked at the SMTP proxy log it showed
2017:04:02-16:28:01 firewall exim-out[16314]: 2017-04-02 16:28:01 1cun2W-0004Ez-60 SMTP error from remote mail server after RCPT TO:<user@receivingdomain.com>: host mail.receivingmailserver.com [old receiving mail server ip]: 451 4.7.1 Try again later 2017:04:02-16:28:01 firewall exim-out[16308]: 2017-04-02 16:28:01 1cun2W-0004Ez-60 ** user@receivingdomain.com P=<prvs=0265f4dfce=user@sendingdomain.com> R=dnslookup T=remote_smtp: SMTP error from remote mail server after RCPT TO:<user@receivingdomain.com>: host aspmx.l.google.com [new new mail server IP]: 550-5.1.1 The email account that you tried to reach does not exist. Please try\n550-5.1.1 double-checking the recipient's email address for typos or\n550-5.1.1 unnecessary spaces. Learn more at\n550 5.1.1 support.google.com/.../ u198si3911947ywg.438 - gsmtp
After speaking with the IT group running their DNS and running the old mail server they said that they were in progress of moving to a google mail server but no accounts had been moved yet.
i was told they set the MX priority in their DNS to the old mail server first and then another priority to the google mail server 2nd for accounts that had been moved. they claim the account in question has not been moved yet and should be delivered to the old mail server and not the new google one.
They claim the i don't have greylisting enabled on the old mail server and that my mail server isn't configured properly because it retried sending the email to quickly. im using the Sophos UTM as a smart host for exchange and can not find anywhere stating what the retry interval is for a server that responds with
451 try again later.
The long shows it did try again immediately. is there anywhere to change the retry interval in the UTM?
Or is it actually the other IT group who may have something configured wrong?
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