MX Record
Also known as: Mail Exchange Record
An MX (Mail Exchange) record is a DNS entry that designates which mail servers handle inbound email for a domain. Multiple MX records can exist with different priority values; sending servers attempt delivery to the lowest-priority host first. MX records are looked up before SMTP delivery; misconfigured MX means mail never reaches the domain.
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Every domain that receives email has at least one MX record. Without one, sending servers do not know where to deliver mail addressed to the domain and fall back to using the A record (the website host) or fail.
Syntax
`example.com. IN MX 10 mail.example.com.`
The `10` is the priority. Lower priorities are tried first. Common pattern: - Primary MX at priority 10 pointing at the main mail server cluster - Backup MX at priority 20 pointing at a secondary cluster
Common patterns
- Google Workspace: `aspmx.l.google.com` at priority 1, plus 4 backup MXes at higher priorities
- Microsoft 365: `<tenant>.mail.protection.outlook.com` at priority 0
- Self-hosted: usually a single MX at priority 10 pointing at `mail.<domain>`
Why MX misconfiguration causes deliverability problems
- Missing MX: mail bounces back to sender
- MX pointing at non-existent host: mail delays then bounces
- Reverse DNS mismatch between MX hostname and sending IP: spam filters flag as suspicious
- Multiple MXes with same priority: sending servers can choose any, which can cause inconsistent behaviour
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Start Free TrialFrequently asked questions
Does Outsolvi require MX changes?+
No. Outsolvi tracks engagement on outbound mail you send via Outlook or Gmail, and if you connect a mailbox (Gmail, Microsoft with read access, or IMAP), it reads replies from there. Your mail keeps arriving at your current provider, so Outsolvi doesn't need MX changes.
How do I check my MX records?+
Use `dig MX <domain>` or MxToolbox's MX lookup. The output lists every MX record with priority.
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Related glossary terms
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