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MX record checker

Which servers take a domain’s mail, in order of priority, whether each has an address, and the faults that lose mail: no MX, an IP in place of a name, an alias, a null MX.

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The answer for allbirds.com

allbirds.comMail goes to 1 server
  1. Priority0allbirds-com.mail.protection.outlook.com52.101.202.156, 52.101.50.1, 52.101.40.28, 52.101.41.192, 2a01:111:f403:f909::3, 2a01:111:f403:f801::, 2a01:111:f403:f909::1, 2a01:111:f403:c946::1cResolves
  • NoteOne mail serverNo second server takes mail if it is down; senders retry for a few days. Hosted mail services often run one name over many machines, so this is common.
  • GoodEvery mail server has an address

Senders try the lowest priority first and move on when it does not answer. Asked of public resolvers (1.1.1.1 and 8.8.8.8) as anyone on the internet sees it, at the moment of the check. A record changed in the last few hours may not show everywhere yet.

One part of allbirds.com’s DNS.The DNS health check reads its name servers, SOA, addresses, CAA and every mail record at once.
Check all of its DNS

What does it check?

No rule in the rulebook covers this, so here is what it reads.

  1. Each mail server and its priority
  2. Whether each name has an address
  3. Whether the domain says it takes no mail at all

Questions

What does MX priority mean?

The lower number is tried first. Servers with the same number share the mail.

Can an MX record point to an IP address?

No. It must name a host, and that host needs its own address record.

What if a domain sends no mail?

A null MX, a single record pointing to “.”, says so, and senders stop trying.

Mail servers in orderExample
  1. 10mx1.example.com203.0.113.25Tried first
  2. 10mx2.example.com203.0.113.26Same number, so it shares the mail with mx1
  3. 20backup.example.net198.51.100.7Tried when neither answers
A domain that sends and takes no mail

example.org. MX 0 .A null MX: senders stop trying at once.

Every MX names a host, never an IP address, and every host has an address of its own. The lowest number is tried first.

The whole site

One page is one part. A read checks every page against the whole rulebook and says what to fix first.

See allbirds.com’s report