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550 Relaying denied. Please use SMTP Authentication.

I got this error ("550 Relaying denied. Please use SMTP Authentication") during e-mail sending. Other error that is visible: "553 sorry, that domain isn't in my list of allowed rcpthosts".

My configuration had the following entries in DNS records:

Above records (in theory) should be sufficient to safely send an email. But it not worked for some recipients.

I have to add the following records to make sending e-mail pass:

Above TXT record defines IP from A record as the only allowed IP that can send emails from your DNS domain ("-all" flag is important when many conditions are defined, not the case here).