Venture Lab Browser domain check vs MXToolbox: what each one can see
MXToolbox is a long-running, widely used set of server-side email and DNS diagnostics. The free Domain Watch check runs in your browser. Because they run in different places, they can see different things.
How each one works
- MXToolbox runs lookups on its own servers. Its MX Lookup page says the lookup goes directly to the domain's authoritative name server, so record changes show up immediately. Its Diagnostics connect to your mail server, verify reverse DNS, run a simple open-relay test and measure response time. Each MX IP can also be checked against more than 100 DNS-based blocklists. Paid plans (its "Delivery Center") add monitoring, DMARC report processing, blocklist monitoring and inbox placement.
- The free Domain Watch check runs in your browser. It asks public DNS-over-HTTPS resolvers (Cloudflare, with Google Public DNS as a fallback) for A, AAAA, MX, NS, TXT and CAA, and the
_dmarcTXT record. It reads the registration expiry through RDAP via rdap.org. There is no backend: only the domain name leaves your device.
Side by side
| Domain Watch (free browser check) | MXToolbox (free lookups) | |
|---|---|---|
| SPF and DMARC parsing | Yes, with plain-language findings | Yes (SPF Record Check, DMARC Check) |
| Several records in one view | One run shows DNS, SPF, DMARC, CAA, DNSSEC flag and expiry | A tool per record type, plus the SuperTool, which combines MX, DNS, blocklist and SMTP diagnostics |
| Freshness | Answers come from public recursive resolvers and can be cached up to the record's TTL | MX Lookup queries the authoritative server |
| Mail server connection, open relay | No (a browser cannot open SMTP connections) | Yes (Diagnostics) |
| Blocklists | No | Yes |
| Registration expiry | Yes, via RDAP | Yes (Whois Lookup) |
| TLS certificate expiry | No (browsers do not expose certificates to pages) | Not one of the lookups compared here; see its tool list |
| Who sees the domain | The public resolvers and rdap.org; no Venture Lab server | MXToolbox's servers |
| Account | None | Lookups without one; monitoring needs an account |
When to use which
- For a quick health check of a domain's DNS and email policy in one view, with nothing sent to a third-party backend, use the browser check.
- When you need SMTP diagnostics, blocklist status, authoritative-server answers or ongoing monitoring, use MXToolbox or a similar server-side service.
Checking the same domain in both is a good way to confirm a fix.
MXToolbox is a trademark of MXToolBox, Inc. It is not affiliated with Venture Lab 10; the name is used only for comparison. Details are from MXToolbox's public pages as of 2026-10-17 and may change. Check them on its site.
Try it free: Free DNS, SPF and DMARC checker
Type a domain to see its public DNS records, SPF and DMARC problems, CAA, DNSSEC and when the domain registration expires.
Open the free tool →About the product: Domain Watch
The tool runs in your browser; only the domain name is sent to public DNS-over-HTTPS and RDAP services. No signup.
Sources
Venture Lab 10 is independent. Other product and service names are used only to describe compatibility or for comparison, and are trademarks of their owners.