FCrDNS check
Forward-confirmed reverse DNS means an address's PTR name resolves back to the same address. Many mail servers reject mail from servers that fail it. Check one address or a list, with each step shown.
Lookups go to Cloudflare's public DNS (1.1.1.1). Nothing is sent to Helpnyx.
How to use it
Three steps
- Enter the address. Usually your mail server's public IP address.
- Read each step. First the PTR name for the address, then the A or AAAA records for that name.
- Fix a failure. Ask the holder of the address block to set the PTR, and make sure the name's A or AAAA record points to the same address.
Questions
Good to know
Why do mail servers care?
Spammers often send from addresses without proper DNS. Gmail, Outlook and others check FCrDNS and may reject or junk mail from servers that fail it.
What if there are several PTR names?
The check passes if any of the names resolves back to the address. One clean PTR record is best.
Who answers these lookups?
Cloudflare's public DNS service (1.1.1.1), asked directly by your browser.
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IPAM Enterprise keeps every /24, block, customer and circuit in one portal, and checks each assignment for overlaps before it is saved.