MX records tell the world where to deliver email for your domain. Without a working MX record you cannot receive replies, and for cold email that is a problem, because replies are the whole point. Receiving servers also sometimes check that a sender's domain can receive mail, so a missing MX record can hurt how your outbound is treated.

Check yours with the free Rhycon email deliverability checker, which looks up your MX records and flags common problems.

What an MX record is

An MX (mail exchanger) record is a DNS entry that names the server that accepts mail for your domain. Each one has a priority number. Lower numbers are tried first, and higher numbers are backups. For example, Google Workspace now uses a single record pointing to smtp.google.com with priority 1, and older setups use five ASPMX records at priorities 1 to 10. Microsoft 365 uses a hostname like yourdomain-com.mail.protection.outlook.com.

Why MX matters for cold outreach

• You need to see replies. If MX is missing or wrong, replies bounce and prospects think you ignored them.

• Bounces are visible. A "no such domain or mailbox" bounce is a delivery failure that your sending platform tracks, and a pattern of them hurts reputation.

• It is a basic trust signal. A domain that sends mail but cannot receive it looks unusual to filters.

Common MX mistakes

1. No MX record at all. Common on freshly bought domains. Mail may fall back to the domain's A record, which is rarely what you want.

2. Old provider records left in place. After moving mail from one provider to another, the old MX records can still receive mail, and you never see it. Remove them.

3. MX pointing at an IP address. MX records must point to a hostname, not an IP.

4. MX pointing at a CNAME. The standard says MX targets should not be aliases. Some servers cope, some do not.

5. Mixed providers. Google and Microsoft records on the same domain split your mail between two systems.

6. Wrong priorities. A backup server with the lowest number gets the mail first.

When a domain should have no inbox

Some domains are not meant to receive mail, such as a domain you only use for web traffic. You can publish a "null MX" record, which is 0 . with priority 0 and a single dot as the target. It tells senders clearly that the domain does not accept mail. Do not do this on a domain that sends cold email, because you want replies.

How to set up MX for a new sending domain

1. Create the mailbox with your provider (Google Workspace or Microsoft 365).

2. Copy the MX records the provider gives you into your DNS host. Delete any existing MX records first.

3. Wait for DNS to update, then send a test email to the address and confirm it arrives.

4. Add SPF, DKIM and DMARC. See our guides to SPF, DKIM and DMARC.

5. Re-run the checker to confirm all four pass.

Doing this for 10, 20 or 50 domains by hand is slow and easy to get wrong. If you would rather not, see Rhycon's managed infrastructure, which uses Rhycon-owned domains and mailboxes for your outreach.

MX record FAQs

Can I have more than one MX record?

Yes. Multiple records give you backups. The lowest priority number is tried first.

Do I need MX records to send email?

Technically no, but in practice yes. You need them to receive replies and bounces, and filters like senders who can receive mail.

How long do MX changes take?

Usually minutes, up to a few hours. Lower the TTL before a migration to speed it up.

What is a null MX record?

A record with priority 0 and a dot as the target. It says a domain does not accept email.