MX record lookup
MX records tell other mail servers where to deliver mail for a domain. Enter a domain and you get the hosts with their priorities, the addresses each one resolves to, and a plain reading of anything that would stop delivery.
What an MX record does
MX stands for mail exchanger. It names the hosts that accept mail for a domain. When someone writes to an address at your domain, their server asks DNS for the MX list first and only then opens an SMTP connection to whatever it finds. With no MX record the domain accepts no mail: the sender either bounces the message or, under the old fallback rule, tries the domain's A record.
Reading the priority
The number in front of each host is its priority, and lower wins. A sender tries the lowest number first and moves down the list when a host does not answer. Equal numbers spread the load across hosts. A single MX works, but leaves no margin: while that host is down, messages wait in senders' queues and eventually bounce.
What usually breaks
Three failures account for most of it. The MX names a host with no A or AAAA record, so delivery stops immediately. The MX resolves into private space such as 10.x or 192.168.x, which nothing outside your network can reach. Or the record is a single dot — RFC 7505 null MX, an explicit statement that the domain accepts no mail. Each shows up as its own line in the report.
Frequently asked questions
- Mail is not arriving even though the MX record exists. Why?
- Most often the MX host does not resolve to an address, or resolves into private space. Check the address column below: an empty one means the host has no A or AAAA record and delivery cannot happen.
- How many MX records should a domain have?
- At least one, in practice two or more. A backup host at a higher priority number keeps accepting mail while the primary is unavailable. Large mail providers typically publish between two and five.
- What does an MX record of '.' mean?
- It is the RFC 7505 null MX: the domain declares that it accepts no mail. Senders reject messages immediately instead of retrying for days. It is the correct setting for a domain used only for a website.
- How long do MX changes take to apply?
- As long as the record's TTL. Until the receivers' resolvers drop the cached answer, some mail still goes to the old host. The DNS propagation page shows which resolvers already see the change.