# MX record An MX (mail exchanger) record says which servers receive email for a domain. When someone sends a message to you@example.com, their mail server looks up example.com's MX records and delivers to the server with the lowest priority number, trying the others if it can't get through. - Record type: MX - Type number: 15 - Used for: Email - How common: Everyday - Defined in: RFC 1035, RFC 5321, RFC 7505 ## Format ``` IN MX ``` | Field | What it means | Accepted values | | --- | --- | --- | | Name | The domain that receives the email: `@` for addresses like you@example.com. | A host name. | | TTL | How long senders may cache the answer. | Seconds; 3600 is typical. | | Priority | Order of preference. Lower numbers are tried first; equal numbers share the load. | 0 to 65535. Only the order between your records matters: 1 and 5 behave the same as 10 and 50. | | Mail server | The host that accepts the mail. | A host name with its own A or AAAA record. Not an IP address, not a CNAME. `.` with priority 0 means the domain takes no email. | ## Examples ### Google Workspace ``` @ 3600 IN MX 1 smtp.google.com. ``` Google's current setup is a single MX. Older setups list five aspmx servers with priorities 1, 5, 5, 10, 10; both work. ### Microsoft 365 ``` @ 3600 IN MX 0 example-com.mail.protection.outlook.com. ``` The host name is your domain with dots replaced by hyphens; copy it from the Microsoft 365 admin centre. ### Primary and backup ``` @ 3600 IN MX 10 mx1.example.net. @ 3600 IN MX 20 mx2.example.net. ``` Senders try mx1 first and fall back to mx2. ### A domain that never receives email ``` @ 3600 IN MX 0 . ``` A null MX. Senders bounce mail straight away instead of retrying for days. Pair it with an SPF of v=spf1 -all and a DMARC p=reject. ## How mail finds your server The sending server asks DNS for the MX records of the part after the @. It sorts them by priority, looks up the A or AAAA record of the first host, and connects to it on port 25. If that fails, it tries the next. If a domain has no MX records at all, senders fall back to its A record, which is rarely what anyone wants. MX records only control receiving. Which servers may send as your domain is set by [SPF](https://lemon.domains/dns-records/spf), [DKIM](https://lemon.domains/dns-records/dkim) and [DMARC](https://lemon.domains/dns-records/dmarc). ## Changing email providers - Lower the MX TTL to 300 a day before. - Add the new provider's MX records and remove the old ones at the same time; mixing providers splits your mail. - Update SPF to include the new provider and set up its DKIM key. - Keep the old mailboxes open for a few days to catch mail from senders with cached records. ## TTL 3600 is the usual choice. Lower it to 300 before switching providers. ## Common mistakes - Pointing an MX at an IP address. It must be a host name. - Pointing an MX at a name that is a CNAME. The standard forbids it and some senders refuse to deliver. - Leaving the old provider's MX records next to the new ones, so some mail lands in the old mailbox. - Adding MX records on a subdomain (mail.example.com) when you meant the domain itself (@). - Treating priority as a percentage. It's an order: the lowest number gets all the mail while it's up. ## At your DNS host - Most dashboards have a separate Priority field; put only the host name in the value. - Route 53 puts both in one value: 10 mail.example.com. - Namecheap: under Advanced DNS, set Mail Settings to Custom MX to add your own. - Cloudflare: MX records are never proxied, and the mail server's own A record must be DNS only (grey cloud). ## Questions ### What does MX stand for? Mail exchanger: the server that exchanges (accepts) mail for the domain. ### Do lower or higher MX priorities win? Lower. A priority 1 server is tried before a priority 10 server. Servers with the same number share the mail. ### Can I have email without an MX record? Senders fall back to the domain's A record, but almost no web server accepts mail, so in practice no. Every domain that receives email needs MX records. ### Does the MX record affect sending email? No. MX only controls where mail to your domain is delivered. Sending is covered by SPF, DKIM and DMARC. ## Related - [SPF record](https://lemon.domains/dns-records/spf.md) - [DKIM record](https://lemon.domains/dns-records/dkim.md) - [DMARC record](https://lemon.domains/dns-records/dmarc.md) - [TXT record](https://lemon.domains/dns-records/txt.md) - [MTA-STS record](https://lemon.domains/dns-records/mta-sts.md) - [A record](https://lemon.domains/dns-records/a.md) Interactive version with a record checker and live lookup: https://lemon.domains/dns-records/mx