Most sending problems get blamed on copy. Very often the real problem sits in DNS, and MX records are one of the first things to check. They are simple once you know what each part means.
What an MX record is
MX stands for mail exchanger. An MX record is a DNS record that tells other mail servers where to deliver email for your domain. When someone sends mail to you, their server looks up your MX records and delivers to the mail host listed there.
Each MX record has three parts. The priority is a number, and lower numbers are tried first. The host is the mail server address, such as a Google Workspace or Microsoft 365 host. The TTL is how long other servers cache the record before checking again.
Why MX records matter for cold email
Cold outreach is mostly sending, so people ignore MX. That is a mistake for three reasons.
First, replies need somewhere to land. If your sending domain has no working MX records, replies and bounces cannot be delivered back to you properly. Second, receiving mail on a domain looks normal. A domain that can only send and never receive looks disposable to filters and to anyone checking it. Third, many verification and research tools read your MX records to guess your provider and judge whether the domain is set up like a real company.
You can see your own setup in seconds with the free MX Record Checker, which shows each host, its priority, and a plain verdict.
How to check your MX records
- Open the MX checker and enter your domain without www or https.
- Read the list of hosts and priorities. At least one valid host should appear.
- Confirm the hosts match the provider where your inboxes actually live.
- If you recently changed providers, check again after DNS has had time to update.
- Run the wider Email Authentication Checker to see MX next to SPF, DKIM, and DMARC in one report.
Common MX problems and fixes
No MX records at all usually means the domain was bought and never connected to a mailbox provider. Add the records your provider gives you, exactly as written. A mix of hosts from two providers usually means an old setup was never cleaned up, so remove the hosts you no longer use. A single host with a very high priority number is fine, as long as the host itself is correct. If mail arrives but replies bounce, check that the domain on your sending inboxes matches the domain that holds the MX records, and confirm your SPF record covers your sending service.
The short version
MX records tell the world where your mail goes. Cold email domains need them set correctly so replies land, bounces register, and the domain looks real. Check yours before every new campaign, not after something breaks.
FAQ
Do I need MX records to send cold email?
You can send without them, but replies and bounces will not come back properly. Set them up before you send.
What priority should my MX record have?
Use the values your mailbox provider gives you. Lower numbers are tried first, and the exact numbers matter less than having the right hosts.
How long do MX changes take to show?
It depends on the TTL. Many changes appear within an hour, but full propagation can take up to a day.