MX Lookup
See which mail servers accept email for a domain, in what priority order, and which provider is behind them.
What MX records tell you
When a mail server wants to deliver a message to [email protected],
the first thing it does is ask DNS for the MX records of example.com.
The answer is a list of hostnames with priority numbers. Delivery is attempted against the
lowest number first, walking up the list until something accepts the connection.
That makes MX records the fastest way to answer two questions: can this domain receive
email at all, and who actually runs its mailboxes. The second is often the more
interesting one. A domain whose MX records point at
aspmx.l.google.com
is on Google Workspace; one pointing at
*.mail.protection.outlook.com
is on Microsoft 365. This tool fingerprints the provider for you.
What MX records do not tell you
A valid MX record means the domain accepts mail. It says nothing about any
particular mailbox. Every address at a domain — real or invented — shares the
same MX records, so an MX lookup can never tell you whether
[email protected]
exists. That answer requires an SMTP conversation with the mail server, which is what the
paid Mailvalid API does.
MX records also say nothing about whether mail from the domain is trustworthy. For that, check its SPF record, DKIM keys, and DMARC policy.
Frequently asked questions
What is an MX record?
An MX (Mail Exchanger) record is a DNS record telling the internet which servers accept email for a domain. Each record carries a priority number and a hostname. A sending server tries the lowest priority number first and falls back to higher ones if it cannot connect.
What does the priority number mean?
Lower is preferred. A record with priority 10 is tried before one with priority 20. Records sharing the same priority are load-balanced between. The absolute values are irrelevant — only their order matters, so 1 and 2 behave exactly like 10 and 20.
What happens if a domain has no MX record?
Senders fall back to the domain's A record and attempt delivery there — this is called an implicit MX. It usually works, but it is fragile and non-obvious. If the domain has neither an MX nor an A record, mail to it hard-bounces every time.
What is a null MX?
A single MX record of '0 .' is a null MX, defined in RFC 7505. It explicitly declares that the domain accepts no email at all. Senders reject the message immediately instead of retrying for days. It is the correct configuration for a domain you only use for a website.
Does having valid MX records mean an email address is deliverable?
No. MX records prove the domain can receive mail; they say nothing about whether a specific mailbox exists. [email protected] and [email protected] share the same MX records. Confirming an individual mailbox requires an SMTP check, which is what the Mailvalid API performs.
Why do I see several MX records for one domain?
Redundancy. If the primary mail server is unreachable, senders try the next one rather than queueing or bouncing. Most providers publish two or more. A domain with a single MX record has a single point of failure for all inbound email.
More free tools
Email Checker
Validate syntax, MX and disposable status for any address.
SPF Checker
Parse SPF and count the RFC 7208 DNS lookups.
DKIM Checker
Find DKIM selectors and check key strength.
DMARC Checker
Inspect your DMARC policy and reporting setup.
Disposable Checker
Detect throwaway and temp-mail domains.
Blacklist Checker
Check an IP or domain against DNS blocklists.
Need to verify a whole list?
This tool stops at DNS. The Mailvalid API confirms whether an individual mailbox actually exists over SMTP — in bulk, with 95%+ accuracy. Start with 100 free credits, no credit card.