About this tool
MX (mail exchanger) records tell sending servers where to deliver e-mail for a domain. This tool lists them in delivery order and resolves every mail server to its IPv4 and IPv6 addresses, so you can see whether each one is actually reachable.
You can paste an e-mail address; only the part after the @ is used.
How to read the results
Preference: senders try the lowest number first and fall back to higher numbers if it is unavailable. Equal numbers are used in random order to share load.
Null MX (0 .) is a deliberate statement that the domain receives no mail (RFC 7505). No MX at all makes senders fall back to the domain's A record, which rarely points at a mail server.
Problems flagged: MX targets that are aliases (CNAME), that do not exist, that have no address, or that resolve to private addresses.
Limitations
- This checks DNS only. It does not connect to the mail servers on port 25, because most hosting networks block outbound SMTP.
- An MX record pointing to a working server does not show whether that server accepts mail for the domain or whether mailboxes exist.
Frequently asked questions
Why do Google Workspace or Microsoft 365 domains show only one MX?
Large providers put many servers behind one host name, so a single MX (for example smtp.google.com or *.mail.protection.outlook.com) is normal and redundant.
Can an MX record point to an IP address?
No. The target must be a host name with A or AAAA records. Some senders tolerate an IP, but it violates the standard and fails with many.
How quickly do MX changes take effect?
Senders cache MX records for their TTL. Lower the TTL a day before a migration, then change the records.
Do backup MX servers still make sense?
Only if they accept mail for your domain and apply the same spam filtering. Poorly filtered backup MX hosts are a well-known route for spam; hosted mail services usually do not need them.
What is an MX record?
A DNS record naming the server that receives e-mail for a domain.
Is a lower MX number better?
Lower means higher priority: it is tried first.
Can a domain have no MX record?
Yes. Senders then try the domain's A record, which rarely works for mail.