Whether there are any
No MX records means the domain cannot receive email. We also spot domains that do not exist and “null MX” records that deliberately refuse mail.
Free tool
MX record lookup
See where a domain’s email is delivered: the mail servers in priority order, who runs them, and whether each one can actually be reached.
Nothing is stored. Works with any domain, not just ours.
What it checks
What the lookup shows
MX (mail exchanger) records tell the rest of the internet which servers accept email for a domain.
Priority order
Senders try the lowest number first. Records are listed in the order mail will actually be delivered.
Who runs your email
We recognise Microsoft 365, Google Workspace and common filtering services such as Mimecast and Proofpoint from their server names.
Servers that resolve
For the first three servers we check each name has an address, and flag names that do not resolve, CNAMEs and bare IP addresses.
What an MX record does
When someone emails you@yourcompany.co.uk, their mail server looks up the MX records for yourcompany.co.uk to find out where to deliver it. Each record has a priority number and the name of a mail server. The lowest number is tried first; higher numbers are fallbacks if it does not answer.
Microsoft 365 and Google Workspace each need only their own records, because the redundancy is built in behind a single name. If you use an email filtering service, your MX records point at the filter, which then passes clean mail on to your mailboxes.
Reading the results
- One or more servers that resolve: mail has somewhere to go. Check the provider is the one you expect — an old provider still listed is a common cause of missing email.
- No MX records: the domain cannot receive email. That is right for a domain that never receives mail, which should also publish an SPF record of
v=spf1 -all. - A server that does not resolve: its name has no address. Senders that try it first will retry or bounce, so remove or correct it.
- A CNAME or an IP address: MX records should name a host that has its own address record. Most senders cope with a CNAME; many refuse an IP address.
Changing your MX records when you move email
Changing MX records is the moment new email starts arriving at your new provider. Do it once the new mailboxes are ready, lower the record’s TTL a day beforehand so the change spreads quickly, and keep the old service running for a few days to catch anything still in transit. Our answer on keeping your email address when you change provider covers the other records involved, and Autodiscover explains how Outlook finds your mailbox afterwards.
MX only covers receiving. To check that the mail you send is trusted, run the email security checker for SPF, DKIM and DMARC.
Questions
About MX
What does MX priority mean?
It is the order senders try your mail servers in. The lowest number is tried first, and higher numbers are only used if it does not respond. Two records with the same number share the load.
How long do MX changes take to work?
Usually minutes to a few hours, depending on the record’s TTL (time to live) and how long other servers cache it. Lowering the TTL a day before you change the records makes the switch quicker.
Can a domain have no MX record?
Yes, if it never receives email. Without an MX record, some senders fall back to the domain’s own address, so a domain that should not receive mail is better off with a “null MX” record and an SPF record of v=spf1 -all.
Can an MX record point to an IP address or a CNAME?
It should not. The standards say an MX record names a host with its own address record. Many senders refuse to deliver to an IP address in an MX record, and some reject CNAMEs.
Does the MX lookup check whether the mail server is working?
It checks that each of the first three servers has an address in DNS. It does not connect to the servers, so a server that resolves but is switched off or blocking connections will not show as a problem here.
Related tools and guides
Rather have it done for you?
SPF, DKIM and DMARC are set up and monitored for every MyExchangeServer customer. Or send us your results for a second opinion from an engineer.
- Free assisted migration
- No set-up fee, no minimum term
- UK data centres, UK engineers