Monday, October 26, 2015

Messages being bounced (postfix & gmail mail servers)



Sometimes.



It's very confusing. We have a service and you get a confirmation e-mail with a link to confirm your account, etc.



If a user is sending an e-mail from one of their own domains; like moo@moohouse.com or james@bigjamesdean.com or lol@laughterhouse.net then it always reports that it can't find them, or the user doesn't exist.



Now, all this is is a php mail function (from what I understand) and it's sent from our web servers. These web servers are a part of our domain, and we use Google, and have the appropriate SFP & MX entries.




The most common message that I get is a claim that the address does not exist or that it's mistyped, but -- in all of the cases, the e-mail exists & has no extra .'s or spaces, or letters.




The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1
http://support.google.com/mail/bin/answer.py?answer=6596
el5si16864532vdb.30 - gsmtp (in reply to RCPT TO command))





I've tested this with one of my @gmail.com accounts and have not had an issue with it sending me an e-mail.



So, since it tends to have a higher reject rate of these @randomtheirdomain.net here, could it be us or them? Or both?



Edit; I'd like to note that when I set up postfix, I set it up using the postfix's "null client" settings (http://www.postfix.org/STANDARD_CONFIGURATION_README.html#null_client)



I did this because I figured the server would only ever be sending mail, and should not receive and/or do local mail delivery.


Answer



I ended up altering postfix to use TLS and that ultimately solved the problem.


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