BETA

MX Record Inspector

Resolve mail servers, validate reverse DNS, and detect your email provider

🔧 Related Tools

ANALYSIS TOOLS
🔒 Full Checker Complete email deliverability scan: SPF, DKIM, DMARC, MX, blacklists & more. 📨 SPF Check and visualise your SPF record including the full DNS lookup tree. 🔑 DKIM Scan all known DKIM selectors and validate key strength for your domain. 📧 Email Headers Analyse raw email headers to trace delivery path and authentication results. 📬 Bounce Decoder Decode NDR bounce messages and SMTP error codes to diagnose delivery failures. 🦁 BIMI Verify your BIMI logo record and VMC certificate status. 🔐 DNSSEC Validate the DNSSEC chain of trust: DS, DNSKEY, and RRSIG records. 🔒 MTA-STS Check your MTA-STS DNS record and TLS policy file for enforced encryption. 📋 TLS-RPT Validate your TLS-RPT reporting address for email transport encryption reports. 🌍 WHOIS Look up domain registration details via RDAP.
DIAGNOSTIC TOOLS
🚫 Blacklist / RBL Check IPs and domains against major email blacklists and RBLs. 📬 MX Inspector 🌐 DNS Propagation Check DNS record propagation across multiple global resolvers simultaneously.
BUILDER TOOLS
🛡️ DMARC Builder Build a DMARC TXT record with the right policy, RUA/RUF and subdomain options. 🛠 SPF Builder Generate a validated SPF record by selecting your email senders. ✂️ Route 53 Splitter Split long DKIM or SPF TXT records for AWS Route 53's 255-character limit.

📬 MX Record Inspector

Resolve MX hosts, check A/AAAA addresses, validate PTR records, and verify FCrDNS for any domain.

Frequently Asked Questions

Common questions about MX records, mail routing, and reverse DNS.

An MX (Mail Exchanger) record is a DNS entry that tells the internet which servers accept email for your domain. When someone sends you a message, their mail server queries your domain's MX records to find out where to deliver it. You can have multiple MX records with different priority values — lower numbers have higher priority, so if your primary server is unavailable, delivery automatically falls back to the next lowest priority host.

FCrDNS (Forward-Confirmed reverse DNS) is a two-step check. First, a PTR lookup on your mail server's IP returns a hostname. Then, a forward lookup (A record) on that hostname must return the original IP. When both directions agree, it's called FCrDNS and it's a strong signal that the IP belongs to a legitimate mail server. Many spam filters require FCrDNS — a mismatch or missing PTR can result in email being rejected or marked as spam.

A null MX record is a special entry with priority 0 and a target of . (a single dot). It's defined in RFC 7505 as a way for domains that intentionally do not accept email to signal this explicitly. Without a null MX, sending servers may attempt delivery to the domain's A record as a last resort. A null MX immediately tells the sender not to bother, reducing unwanted connection attempts and backscatter spam.

Having multiple MX hosts provides redundancy. If your primary mail server is unreachable, the sending server will try the next lowest-priority host. Priority is set by the number in the MX record — 10 mail1.example.com is preferred over 20 mail2.example.com. Two hosts at the same priority (e.g., both at 10) will be tried in random order, effectively load-balancing delivery. For most organisations, at least two MX hosts are recommended.

A PTR mismatch means your mail server's IP has a reverse DNS record, but when that PTR hostname is resolved forward, it doesn't point back to the same IP. This breaks FCrDNS and is often treated as a red flag by spam filters. Some receiving mail servers will reject connections outright from IPs with no PTR or a mismatched PTR. PTR records are managed by whoever controls your IP address block — typically your hosting provider or ISP — so you may need to request the correct PTR be set through them.