Checker · MX MX lookup: where does this domain’s email go?
An MX record tells senders which servers accept mail for a domain, and in what order. This checker lists them by priority, resolves each server’s address, names the provider when its host names are published, and flags the setups that silently lose mail.
- 10 record types
- Compare 3 resolvers
- Sent only when you click
Check MX records
Enter the domain after the @ in the email address. Each mail server is also looked up for A and AAAA records.
cloudflare-dns.com), Google (dns.google) or Alibaba Cloud (dns.alidns.com) — for the name and record type, nothing else. Checks that follow a chain (SPF includes, MX hosts) send those names to the same service. TapCub’s servers are not involved and store nothing.Subdomains, underscore names such as _dmarc.example.com and international domains all work.
In mainland China, Alibaba Cloud is usually reachable when the other two are not.
Summary
- OK3 mail servers for tapcub.com. Senders try the lowest priority number first.
- NoteThese look like Zoho Mail mail servers (matched against the provider’s published host names).
- NoteSample result: these records were looked up on 2026-11-11 while building this page. Click Look up for live data.
Mail servers
| Priority | Mail server | Addresses | Service | Check |
|---|---|---|---|---|
| 10 | mx.zoho.com | 204.141.43.44 | Zoho Mail | Resolves |
| 20 | mx2.zoho.com | 204.141.43.44 | Zoho Mail | Resolves |
| 50 | mx3.zoho.com | 204.141.43.44 | Zoho Mail | Resolves |
tapcub.com. 600 IN MX 10 mx.zoho.com.
tapcub.com. 600 IN MX 20 mx2.zoho.com.
tapcub.com. 600 IN MX 50 mx3.zoho.com.The same records in the format used by BIND and most DNS panels’ import screens.
Share these inputs: the values go after the # in the link, so they never reach a server.
https://tapcub.com/tools/dns-lookup/mx
Version v1.0Updated Update history
Reading an MX result
Priority, host and whether the host can be reached.
Priority
Lower numbers are tried first. Equal numbers share the load. The values only matter relative to each other: 1/5/10 and 10/20/30 behave the same.
Mail server
A host name, never an IP address or an alias. Hosted services publish theirs: Google Workspace uses smtp.google.com, Microsoft 365 a name ending in mail.protection.outlook.com.
Resolves
Each server needs an A or AAAA record, or senders cannot connect. “Does not exist” or “No address” means mail for that priority is lost or delayed.
No MX or Null MX
No MX: senders fall back to the domain’s own address, usually a web server. Null MX (0 .): the domain says it never receives mail, which is right for domains used only for websites or sending.
An MX check shows where mail is delivered, not whether a particular mailbox exists. That only shows up when you send.
Three steps
No sign-up. One click sends the queries.
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1
Enter a name
A domain, subdomain, URL or email address. Paste an IP address for a reverse lookup.
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2
Pick type and resolver
Common types is the usual start. Choose “Compare all three” after a DNS change to see whether it has spread.
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3
Look up and copy
Read the summary, then copy the zone-file lines or download them. Open the MX, SPF, DMARC or DKIM checker for mail records.
MX rules from the standards
RFC 5321 describes how senders use MX records; RFC 7505 adds the Null MX.
- Sort by preference, try the lowest first, randomise equal ones (RFC 5321 §5.1)
- No MX: treat the domain itself as the mail server (the “implicit MX”)
- An MX target must be a host name with an address record, not an alias (RFC 2181 §10.3)
- Null MX: exactly one record,
0 ., meaning “no mail accepted” (RFC 7505)
| Provider | MX host |
|---|---|
| Google Workspace | smtp.google.com (older setups: aspmx…) |
| Microsoft 365 | <domain>.mail.protection.outlook.com |
| Zoho Mail | mx.zoho.com, mx2, mx3 |
| Tencent Exmail | mxbiz1.qq.com, mxbiz2.qq.com |
| Alibaba Mail | mx1.qiye.aliyun.com … (older: mxhichina.com) |
tapcub.com’s mail servers on 2026-11-11
Three Zoho servers at priorities 10, 20 and 50.
| Priority | Server | Address | Reading |
|---|---|---|---|
| 10 | mx.zoho.com | 204.141.43.44 | Tried first |
| 20 | mx2.zoho.com | 204.141.43.44 | Backup name |
| 50 | mx3.zoho.com | 204.141.43.44 | Backup name |
All three names resolved to the same address that day. That is the provider’s choice; from the outside, the three priorities still give senders three names to try.
MX mistakes that lose email
Usually the record is fine and something else is in the way.
Pointing MX at a CNAME
mail.example.com as a CNAME to a provider looks fine in a panel but breaks the standard; some senders refuse it. Use the provider’s host name directly.
Putting an IP in the MX
MX values must be names. Create an A record such as mail.example.com and point the MX at that.
Leaving the old provider in
After moving to a new mailbox host, old MX records with a lower number keep receiving some mail. Remove them once the move is done.
Where domains show up in your analytics
DNS answers practical questions behind the reports: who sent this traffic, which network a crawler came from, and how the tracking script is served.
Referring domains
Sources lists the sites that send visitors. Look up an unfamiliar one to see whether it resolves and who hosts it before you trust its traffic.
Learn moreBots counted separately
TapCub separates crawlers from people with five layers, one of them hosting networks. A PTR lookup shows the hostname a crawler’s IP publishes.
Learn moreNo CNAME tricks
TapCub does not use CNAME aliasing to make its requests look first-party. The cookie policy lists what else it deliberately does not do.
Learn moreDNS lookup questions
Still have a question?
Chat with the team behind TapCub — we usually reply within a few hours on business days.
How do I find a domain’s mail server?
Look up its MX records: enter the domain above and click Look up. The server with the lowest priority number is the one senders try first.
Does a lower MX priority mean higher priority?
Yes. Senders try the lowest number first and move to higher numbers only if it does not answer. Records with the same number share the mail.
What is a Null MX?
A single MX record of “0 .” defined in RFC 7505. It tells senders the domain accepts no email, so they bounce immediately instead of retrying for days. Use it on domains that only host a website.
Can an MX record point to an IP address or a CNAME?
No. An MX must name a host that has its own A or AAAA record. IP addresses are invalid, and aliases are forbidden by RFC 2181 even though some senders tolerate them.
Update history
New features, fixes and data refreshes for this tool, newest first.
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· v1.0
LaunchedFirst release.
Missing something or found an error? Tell us — requests that come up often go into the next update. All tool updates
From the domain to the visitors it brings
TapCub shows where visitors come from, separates bots from people, and adds live chat on the same snippet. No cookies in the default mode.