The three values that must agree
When opening a connection the sending server introduces itself with EHLO hostname. The recipient can check that claim against two independent pieces of DNS information: the PTR record of the connecting IP (reverse DNS) and the A record of the hostname given. Only when all three agree is the server's identity confirmed:
- IP
1.2.3.4→ PTRmail.example.com mail.example.com→ A1.2.3.4- HELO hostname:
mail.example.com
The second step is the decisive one — it is called FCrDNS (forward-confirmed reverse DNS). A PTR record alone says little, because the IP owner can set it freely. Only the return path proves that both sides are under the same control.
What AnalyzeMy.Email checks
- PTR record of the sending IP — does one exist at all?
- FCrDNS — does the PTR name resolve back to the same IP?
- HELO match — does the hostname given in the SMTP dialogue match the reverse DNS?
- Generic patterns — hostnames suggesting a datacenter default naming scheme
Why this carries so much weight
Reverse DNS is one of the few values a sender cannot set themselves — the PTR record belongs to the owner of the IP block, that is, the hosting provider. That is precisely what makes it meaningful to recipients: whoever has a clean PTR record has a contractual relationship with a provider and is therefore accountable. Botnet operators do not.
The consequences are severe. Large providers sometimes reject connections from IPs without a PTR record outright. Generic hostnames such as vps12345.hoster.com, or names that look like dynamic addresses, frequently lead to spam classification or rejection. Mail from a server without reverse DNS often does not reach Gmail at all.
Setting it up
- Set the PTR at your hosting provider — usually in the customer panel under IP management, not in your own DNS zone.
- Create a matching A record so that FCrDNS resolves.
- Set HELO to the same FQDN — in Postfix via
myhostnameorsmtp_helo_name. - Choose a meaningful name, e.g.
mail.yourdomain.comrather than a provider default. - Don't forget IPv6: if the server also sends over IPv6, that address needs a PTR record too. Without one, Google rejects.