DNS and Email Diagnostics Website

MXToolbox

MXToolbox is a network diagnostics website for checking MX records, DNS records, email blacklists, SMTP behavior, SPF, DKIM, DMARC, BIMI, MTA-STS, TLS reporting, WHOIS data, and other internet infrastructure signals.

Official site

mxtoolbox.com is the main public website for MXToolbox.

Core tool

The SuperTool combines MX, DNS, blacklist, SMTP, domain, and network lookups in one searchable interface.

Common audience

Email administrators, DNS operators, support teams, web hosts, and security teams use MXToolbox to troubleshoot deliverability and infrastructure issues.

MXToolbox provides DNS, email, blacklist, SMTP, domain, and network diagnostic tools for administrators and technology teams.View logo icon asset on MXToolbox

What MXToolbox is

MXToolbox official site is a network diagnostics website focused on email, DNS, blacklist, and internet infrastructure checks. Its SuperTool lets users enter a domain, IP address, or hostname and run targeted lookups such as MX, SPF, DKIM, DMARC, blacklist, SMTP, WHOIS, DNS, and HTTPS checks.

SuperTool lookups

The SuperTool is the center of the site. A user can type a normal domain name for a default lookup or prefix a command such as mx:, blacklist:, dmarc:, spf:, smtp:, whois:, a:, txt:, or https: to force a specific test. Results link to related checks so a troubleshooting session can move from one signal to the next.

Email deliverability checks

MXToolbox is widely used when email is bouncing, delayed, marked as spam, or failing authentication. MX records show where mail should be delivered, SMTP checks inspect server behavior, blacklist checks identify reputation issues, and SPF, DKIM, DMARC, BIMI, MTA-STS, and TLSRPT lookups help diagnose modern email security configuration.

DNS and network tools

The network tools page lists many non-email checks as well: A, AAAA, CNAME, TXT, SOA, PTR, SRV, DNSSEC-related records, certificate checks, ASN lookup, ARIN information, ping, traceroute, TCP port status, HTTP, HTTPS, DNS propagation, subnet calculation, and domain health reports.

Blacklist and reputation context

A blacklist check can show whether an IP address or host appears on DNS-based email blocklists. That result is useful context, but it is not the whole story. A listed IP may be shared, recently reassigned, misconfigured, compromised, or temporarily flagged, so administrators still need to confirm the source and remediation path.

Who uses MXToolbox

MXToolbox is used by system administrators, email deliverability specialists, web hosts, MSPs, help desks, DNS operators, security teams, and small business owners. It is especially useful when a problem crosses boundaries between DNS, mail hosting, spam filtering, certificates, and network reachability.

Limits and interpretation

Diagnostic tools can point toward a problem, but they do not always explain the cause. DNS propagation delays, split-horizon DNS, cloud email routing, third-party filters, cached records, and provider-specific policies can all affect results. MXToolbox reports should be paired with mail logs, DNS provider data, and receiving-server error messages.

Why it matters

Email and DNS problems are easy to misread because a single symptom can involve many systems. MXToolbox matters because it brings common checks into one browser-based workflow, helping teams quickly test the records and reputation signals that make domains, websites, and email services work.

WHOIS domain data

Data pulled: May 23, 2026View current WHOIS record

Domain: mxtoolbox.com
IP address: 3.167.56.87
Registrar: Network Solutions, LLC
WHOIS server: whois.networksolutions.com
Referral URL: http://networksolutions.com
Created: September 28, 2004
Updated: December 13, 2023
Expires: September 28, 2026
Nameservers: ns-1736.awsdns-25.co.uk (205.251.198.200); ns-984.awsdns-59.net (205.251.195.216); ns-495.awsdns-61.com (205.251.193.239); ns-1320.awsdns-37.org (205.251.197.40)
Domain status: clientDeleteProhibited https://icann.org/epp#clientDeleteProhibited; clientTransferProhibited https://icann.org/epp#clientTransferProhibited; serverDeleteProhibited https://icann.org/epp#serverDeleteProhibited; serverTransferProhibited https://icann.org/epp#serverTransferProhibited
Contact privacy: Registrant contact is listed through PERFECT PRIVACY, LLC.

Key concepts

MX recorda DNS record that tells other mail servers where to deliver email for a domain.
Blacklist checka lookup that tests whether an IP address or host appears on email reputation blocklists.
Email authenticationDNS-based controls such as SPF, DKIM, and DMARC that help receivers evaluate whether mail is authorized.
Domain healtha combined view of DNS, mail, web, and reputation checks that can reveal configuration or reachability issues.

Website features

Run MX, DNS, WHOIS, SMTP, blacklist, SPF, DKIM, DMARC, BIMI, MTA-STS, and TLSRPT checks.
Inspect A, AAAA, CNAME, TXT, SOA, PTR, SRV, DNSSEC, certificate, ASN, ARIN, HTTP, HTTPS, ping, and traceroute signals.
Use command-style SuperTool prefixes to force a specific test.
Review chronological lookup history and follow related diagnostic links from one result to the next.

Common misconceptions

A single blacklist result does not automatically prove that a domain owner caused abuse.
Passing MXToolbox checks does not guarantee email delivery, because receivers can apply private filtering rules.
DNS records can be correct at one resolver and stale at another during propagation or caching windows.
MXToolbox diagnoses public signals; private provider logs and bounce messages are still important.

Open questions

How can email diagnostic tools better explain which failures are urgent and which are harmless warnings?
What is the best way to show blacklist context without encouraging overreaction to noisy reputation data?
How should tools surface DMARC, BIMI, MTA-STS, and TLS reporting guidance for non-specialists?
Will AI-assisted troubleshooting make DNS and email errors easier to resolve, or will it hide important protocol details?