MX Lookup
See which mail servers accept email for a domain.
An MX record tells the rest of the internet which servers accept email for a domain. A sending server looks up the MX records for the recipient's domain, sorts them by preference, and tries the lowest number first. Without an MX record there is nowhere to deliver, and mail to the domain bounces.
The preference number is a priority, and the ordering is counter-intuitive: 10 is preferred over 20. Publishing several records at different preferences gives you failover, since a sender that cannot reach the primary moves down the list. Publishing several at the same preference distributes load between them instead.
MX records are only the first of four things that decide whether your email arrives. They establish where mail is delivered; SPF says which servers may send on your behalf, DKIM signs the messages, and DMARC tells receivers what to do when those checks fail. A domain with perfect MX records and no DMARC policy is still trivially spoofable.
What this tool does
Priorities in order
MX records carry a preference number, and lower wins. The list shows the order senders will actually try, not just the set.
Identify the provider
The hostnames name the platform: Google Workspace, Microsoft 365, Proton, Zoho or a self-hosted server are all recognisable at a glance.
Confirm a migration
After moving providers, the old servers must be gone from this list. Leaving them in place silently splits incoming mail between two systems.
Start of the delivery check
MX records say where mail goes. SPF, DKIM and DMARC decide whether it is trusted — check those next.
Frequently asked questions
What is an MX record?
An MX ("mail exchanger") record names a server that accepts email for a domain, along with a preference number. Sending servers look up MX records for the recipient domain and connect to them in preference order to deliver a message.
What does the MX priority number mean?
It is a preference, and lower numbers are tried first. A record with priority 10 is used before one with priority 20, which only receives mail if the first is unreachable. Records sharing a priority are treated as equal and selected between at random, spreading the load.
Why is my email bouncing when I have MX records?
MX records only say where to deliver. Mail still bounces if the named server refuses the connection, does not recognise the recipient address, or rejects the sender on SPF, DKIM or DMARC grounds. Check the bounce message — it usually quotes the receiving server's own reason.
Can a domain have no MX record and still receive email?
There is a legacy fallback where a sender with no MX answer may try the domain's A record, but you should not rely on it: many modern senders skip it, and receivers increasingly treat a missing MX as a signal the domain does not do email. If the domain should receive mail, publish MX records.
How many MX records should I have?
Whatever your provider specifies — usually two to five. Google Workspace and Microsoft 365 each publish their own recommended set, and the right answer is to match it exactly. Extra records pointing at servers you no longer use are worse than none, because some mail will be delivered there.
Should MX records point at a hostname or an IP address?
A hostname, always. The specification requires the MX target to be a name with its own address records, and an IP address in an MX record is invalid — some senders reject it outright while others silently fail, which makes it a difficult fault to diagnose.
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