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MailFleet

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Reverse DNS checker — PTR records & FCrDNS validation

Enter your outbound SMTP IPv4 address to look up PTR reverse DNS, verify forward-confirmed rDNS (FCrDNS), and optionally check HELO/EHLO hostname alignment.

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At a glance

What it is
IPv4 PTR lookup with forward-confirmed rDNS validation and optional HELO/EHLO alignment checks.
Who it is for
SMTP operators, deliverability teams, and MailFleet users validating new sending IPs.
Main capabilities
PTR query, FCrDNS badge, forward A/AAAA, HELO compare, multi-PTR warning, captcha, rate limits.
Platforms
Browser-based reverse DNS check on mailfleet.app (IPv4) when the live service is available.
Responsible use
Checks public DNS only. Request PTR changes through your host or email provider.

Reverse DNS validation

PTR lookup, forward-confirmed rDNS (FCrDNS), and optional HELO/EHLO alignment for outbound SMTP IPs.

Sending IP

Security verification

Required to prevent automated abuse of the public DNS checker.

Verification challenge

Capabilities

Validate rDNS before you send

Missing or misaligned PTR records are a common cause of deferrals and spam-score hits on strict receivers.

  • PTR lookup

    Query in-addr.arpa for the PTR hostname assigned to your sending IP.

  • FCrDNS validation

    Confirm the PTR hostname forward-resolves back to the same IPv4 address.

  • Forward A/AAAA

    Show forward DNS answers for each PTR hostname.

  • HELO alignment

    Optional HELO/EHLO hostname check against PTR for SMTP identity consistency.

  • Multi-PTR detection

    Flag multiple PTR records on one IP — often discouraged for mail servers.

  • Abuse-resistant

    Image captcha, session verification, and per-IP rate limits for public use.

How to use

Five steps to valid reverse DNS

  1. 1

    Enter sending IP

    Use the IPv4 address your SMTP server connects from — not your domain.

  2. 2

    Add HELO (optional)

    Paste the EHLO/HELO hostname from SMTP diagnostics or provider docs.

  3. 3

    Solve captcha

    Complete the image challenge before running the lookup.

  4. 4

    Review PTR & FCrDNS

    PTR must exist and forward-resolve to your IP for FCrDNS pass.

  5. 5

    Fix with provider

    Request PTR updates from your host/ISP if misaligned, then re-check.

What is reverse DNS?

Reverse DNS maps an IP address to a hostname via PTR records in in-addr.arpa (IPv4). Mail receivers often check that your sending IP has a PTR record and that the hostname forward-resolves back to the same IP — forward-confirmed reverse DNS (FCrDNS).

Your SMTP HELO/EHLO hostname should align with the PTR name. Mismatches can increase spam scores or cause connection issues with strict providers.

Who controls PTR records?

PTR is controlled by whoever owns the IP block — typically your VPS host, dedicated server provider, or ISP. You cannot set PTR in your domain DNS unless you own the IP range.

When moving providers, request PTR updates before sending production mail from a new IP.

  • Dedicated IP from ESP — they set PTR to mail.yourdomain.com
  • VPS — open ticket with host to set PTR
  • Shared pools — PTR may be generic and not customizable

What this tool does not do

IPv4 only in this checker. It does not open SMTP connections or verify banner/STARTTLS on the host.

FCrDNS for IPv6 uses ip6.arpa — not covered here; use your provider’s IPv6 rDNS tools.

Key takeaways

  • PTR is set by your IP owner — not your domain DNS unless you control the IP block.
  • FCrDNS requires the PTR hostname to resolve forward back to your sending IP.
  • HELO/EHLO should match or relate to the PTR hostname.
  • Pair rDNS checks with blacklist and SMTP diagnostics before production sends.

For regulatory context on commercial email in the United States, see the FTC CAN-SPAM compliance guide.

Delivery note: MailFleet helps users manage campaigns through their own sending providers. Delivery outcomes depend on sender reputation, DNS authentication, content quality, recipient engagement, list quality, provider rules, and mailbox filtering systems.

Reverse DNS checker FAQ

Your hosting provider, ISP, or email provider for dedicated IPs. Request PTR changes through their support panel or ticket system.

Get started

Validate SMTP setup in MailFleet

SMTP diagnostics, provider profiles, and campaign logs — confirm IP and hostname alignment before send.

Download MailFleetSMTP diagnostics

Available on

  • Windows 10+
  • macOS 12+
  • Linux (DEB & RPM)

Same desktop experience across every platform — one workflow for your entire team.