Score:0

550 [REMOTE IP] is not allowed to send mail from [MY DOMAIN] (in reply to RCPT TO command)

za flag
NLS

Please note the brackets in the title. Mail server works ok (for years) - even when I tightened security months ago (SPD is "a mx -all" not even "~all"). Sends and receives ok.

BUT: A user of mine is sending an email to a specific remote recipient and the mail is not delivered with this error above. Thing is, that it seems like a remote mail server (I am positive it is the recipient's ISP mail server), is trying to send email as MY domain, which of course is not allowed, hence the error (that the ISP mail IP is not allowed to send as my domain). Note that the recipient domain is NOT the same as the ISP, although they probably registered it in their ISP registrar.

I suspect their ISP mail server gets all mail, including mail of their clients' registered domains, maybe spam-filter them and then relay them as the original domain but sent from the ISP mail server IP.

This to me looks like misconfiguration on their side (which is what I told my user). Am I correct to assume that?

Score:1
in flag

You are correct, that's a misconfiguration on the recipients side. There is nothing you can do but reach out to the recipient in other ways and tell him about this issue.

mangohost

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