MxToolbox Alternative: Free MX, Blacklist and Email DNS Checks

MxToolbox is the first stop for many people debugging email: look up MX records, check a blacklist, test an SMTP server. If you are looking for an alternative, you may want a simpler interface, a tool that does not need a long list of commands, or checks that sit next to website diagnostics. This page compares MxToolbox with SiteDownCheck's email-related tools and says plainly where the larger tool is the better choice.

MxToolbox details come from its home page and SuperTool page as read in October 2026. We did not verify its pricing, monitoring features or limits, so we do not make claims about them. Check their site for current plans. Our details come from how our tools work.

What MxToolbox does best

MxToolbox's SuperTool is a single input box with a long list of lookup commands. The page lists, among others: a, aaaa, cname, mx, txt, soa, ptr, spf, dkim, dmarc, bimi, mta-sts, tlsrpt, blacklist, asn, arin, whois, http, https, tcp, smtp, ping, trace and a DNS server health check. Its MX lookup page says it lists a domain's MX records in priority order, queries the domain's authoritative name server directly, and then runs diagnostics: it connects to the mail server, checks reverse DNS, runs a simple open relay test and measures response time. The same page says it checks the MX IP addresses against 105 DNS-based blacklists.

That breadth is the strength. A single place offers SMTP conversation tests, ping and traceroute, which our tools do not. If you have an inbound mail problem and need to see whether port 25 answers on the mail server, MxToolbox does that.

What SiteDownCheck does

Our email tools are narrower and focused on DNS-based configuration.

• The MX lookup lists the mail servers for a domain with their priorities.
• The email DNS checker reviews SPF, DMARC and DKIM in one run. For SPF it flags multiple records, a missing or permissive all mechanism and an estimated DNS lookup count over the limit of 10. For DMARC it reports the policy and whether an rua reporting address is set. For DKIM it tries 16 common selector names; if you use a custom selector, a "not found" result is expected. It also notes an MTA-STS record if present, and returns a score and grade with tips.
• The SPF record checker focuses on SPF alone.
• The blacklist checker queries 7 IP-based DNS blocklists (Spamhaus ZEN, SpamCop, UCEPROTECT Level 1, PSBL, DroneBL, S5H and NiX Spam) and, for a domain, 2 domain lists (Spamhaus DBL and SURBL).
• The email deliverability test and the DNS checker cover the surrounding checks.

Side-by-side

When to use which

Use MxToolbox when you need a wide net for a mail problem: you want to test the SMTP server, query many blocklists at once, run a traceroute, or look up specific records like BIMI. It is the more complete mail troubleshooting bench.

Use our email DNS checker when you want a quick health read on a domain before sending campaigns or after changing providers. It tells you in one view whether SPF, DKIM and DMARC are present and sane, and the tips are written as actions. SPF, DKIM and DMARC: the complete guide explains the details.

Use our blacklist checker for a fast first check of the major lists. A clean result on 7 lists does not prove you are clean everywhere, because mailbox providers also use private reputation systems that no public checker can see. A listing on a well-known list is a strong lead; read the email blacklist removal guide for next steps.

A combined workflow for "my email is going to spam"

1. Run the MX lookup to confirm the domain points at the provider you think it does. The MX records guide explains priorities.
2. Run the email DNS checker. Fix a missing or broken SPF, DKIM or DMARC record before anything else, since authentication failures are the most common cause.
3. If SPF reports too many lookups, follow fix SPF too many DNS lookups.
4. Run the blacklist checker on your sending IP and domain.
5. Use MxToolbox, or a similar tool, for SMTP tests, reverse DNS (PTR) and a wider blocklist sweep. The reverse DNS for email guide covers PTR.
6. Send a real message through the email deliverability test and read the result.

Make one change at a time and allow for DNS TTLs before retesting. The DNS checker shows whether public resolvers agree on a changed record.

Honest limits of ours

We do not run SMTP conversation tests, open relay tests, ping or traceroute, and we do not look up BIMI or TLS-RPT records. Our blacklist coverage is much smaller than a 105-list sweep. Our DKIM check can only find selectors from its built-in list. We do not monitor blacklists over time. If you need those, MxToolbox or a similar service is the right tool, and for anything that affects revenue you should also check the reputation dashboards your mailbox providers publish.

Next steps

• Look up records with the MX lookup.
• Check authentication with the email DNS checker.
• Test lists with the blacklist checker.
• Plan your policy rollout using the DMARC rollout guide.
• Read why email goes to spam.

FAQ

Is SiteDownCheck a replacement for MxToolbox?

For basic MX, SPF, DKIM, DMARC and major blacklist checks, it is a quick alternative. For SMTP tests, traceroute and a very broad blocklist sweep, MxToolbox covers more.

Why does your DKIM check say not found?

We test 16 common selector names. If your provider uses a custom selector, the record exists but we will not find it. Look up the exact selector in your provider's setup page.

Does a clean blacklist check mean my email will be delivered?

No. Authentication, content, sending history and private provider reputation all matter. Blacklist checks are one signal.

Do I need an account?

Not for our tools. You need a free account only to create monitors.

Opinions here are our own; verify vendor details yourself. See our editorial policy and disclaimer.