Client sending email and PTR validation is failing
I have a client who uses Microsoft Office 365.
He is sending email to an account that is on our server.
However, he is getting an error like this:
Your message could not be delivered to myemail@domain.com.br
A security check on myhost.com.br failed due to incorrect settings on hostclient.com.br
Can I disable this PTR check?
Is it safe to disable it? To what extent do I compromise my security?
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I didn't think the PTR check would occur if the customer was actually SMTP authenticating. But I could be wrong.
I never enable the PTR check. There are legitimate IPs without rDNS that sent to my customers. However, I will say that there are way more IP addresses without rDNS that send spam as compared to legitimate ones.
Heck I don't even know where the option to block incoming mail from IP addresses withou rDNS exists. Where is this option? I'd presume somewhere in the Exim Configuration, but I don't see it.
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I'm not aware of any PTR checks on email as that isn't something the email system would typically care about. Your message says "a security check" but I'm not seeing anything included about the PTR. Could you paste the entire error message? You also should be able to find more details about the mail transaction in the Exim log at /var/log/exim_mainlog if you search for that sender or the mail ID.
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