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SMTP-PTR-NOT-CONFIRMED

Reverse DNS for the mail server is missing or does not confirm forward

What it means

Receivers expect the sending/receiving host's address to have a PTR whose name resolves back to the same address. Gmail, Outlook.com and Yahoo require it for senders.

How to fix it

  1. 1Ask whoever holds the address block (hosting provider, ISP) to set the PTR to the server's host name.
  2. 2Make sure that host name has an A record with the same address.

Re-check after the change

DNS changes can take up to the record's TTL to be seen; use Re-run on the result page to bypass our 10-minute cache.