MX lookup: check a domain's mail servers
Enter a domain to run an MX lookup. You see every MX record sorted by priority and the mail provider behind them. Free and unlimited, no credits used.
- Free and unlimited
- Records sorted by priority
- Mail provider detected
How to check MX records
An MX record lookup tells you where a domain's email is delivered.
- 1
Enter the domain
Type the part after the @ in an email address, such as example.com.
- 2
Run the MX lookup
We query DNS live and list every mail server with its priority.
- 3
Read the priority
The lowest number is tried first. Higher numbers are backups.
- 4
Check the provider
We name the mail provider, such as Google Workspace or Microsoft 365, so you know which settings apply.
What an MX record does
An MX (mail exchanger) record is a DNS entry that tells other mail servers where to deliver email for a domain. When someone sends a message to you@example.com, their server looks up the MX records for example.com and hands the message to the server listed there.
Each MX record has two parts: a priority number and a mail server hostname. A domain can have several MX records so that mail still arrives if one server is down.
How MX record priority works
Lower numbers win. A sending server tries the record with the lowest priority value first and only moves to higher values if that server does not answer.
Records with the same priority share the load. Google Workspace's current setup uses a single record, smtp.google.com at priority 1, while older setups list five aspmx servers at 1, 5, 5, 10 and 10.
- Lowest value is tried first
- Equal values split traffic
- Higher values act as backups
| Priority | Mail server | Role |
|---|---|---|
| 1 | aspmx.l.google.com | Primary |
| 5 | alt1.aspmx.l.google.com | Backup |
| 5 | alt2.aspmx.l.google.com | Backup |
| 10 | alt3.aspmx.l.google.com | Backup |
| 10 | alt4.aspmx.l.google.com | Backup |
Mail providers our MX record checker detects
| Provider | MX hostname looks like |
|---|---|
| Google Workspace | smtp.google.com or aspmx.l.google.com |
| Microsoft 365 | yourdomain-com.mail.protection.outlook.com |
| Zoho Mail | mx.zoho.com, mx2.zoho.com, mx3.zoho.com |
| GoDaddy | smtp.secureserver.net, mailstore1.secureserver.net |
| Mimecast | *.mimecast.com |
| Proofpoint | *.pphosted.com |
Common problems when you check MX records
No MX record
The domain cannot receive email. Senders may fall back to the A record, but most mail will bounce. Add the records your provider gives you.
Wrong priority
A backup server set to a lower number than the main one gets mail first. Make the primary server the lowest value.
Leftover records after migration
Old provider records left in place split incoming mail between two systems. Remove them once the new provider is live.
Yes, and it is unlimited. MX lookups do not use credits, so you can check as many domains as you like without signing up.
It depends on the record's TTL. Most changes show within an hour, but some resolvers cache records for up to 48 hours. Run the MX record lookup again later if you still see the old values.
Technically yes, but mail will be split between them and messages will seem to go missing. Keep only one provider's records unless you run a deliberate gateway setup like Mimecast in front of Microsoft 365.
MX records control incoming mail. Outgoing deliverability depends on SPF, DKIM and DMARC. That said, some receivers check that a sending domain can receive replies, so a missing MX can hurt.
Point each sending domain's MX records to the same provider as its mailboxes, then add SPF, DKIM and DMARC. Use our domain health checker to test all of them at once.
Further reading
- RFC 5321: Simple Mail Transfer Protocol How mail servers hand off messages and how MX records are used.
- RFC 1035: Domain names The core DNS specification that defines record types and lookups.
- Google email sender guidelines Gmail requirements for authentication, spam rates and unsubscribe links.
Setting up domains for cold email?
We set up domains, mailboxes, MX, SPF, DKIM and DMARC, then warm them up before your first campaign.