When sending a letter using Postfix, a reply letter arrives at mail.ru with an error message of the form:

Final-Recipient: rfc822; ... Original-Recipient: rfc822;... Action: failed Status: 5.0.0 Remote-MTA: dns; mxs.mail.ru Diagnostic-Code: smtp; 503 Valid RCPT command must precede DATA

What is the problem and how to fix it?

  • Check the reverse DNS and MX records of your domain. - pyatak

1 answer 1

At mail.ru this may be the case when the MX record directly indicates the server ip, i.e.

 example.com MX 5 1.2.3.4

instead

 example.com MX 5 mail.example.com. mail A 1.2.3.4