MX Checker

What are MX Records?

MX (Mail Exchanger) records are DNS entries that specify which mail servers are responsible for receiving email on behalf of your domain. When someone sends an email to your domain, their mail server queries your DNS for MX records to determine where to deliver the message.

Without MX records, other mail servers have no way to know where to route messages destined for your domain, and emails will bounce or be undeliverable.

How MX Records Work

The email delivery process relies on MX records in a straightforward way:

1. Sender initiates delivery – When a mail server needs to send email to your domain, it performs a DNS lookup for your MX records.

2. DNS returns your mail servers – The lookup returns one or more mail servers along with their priority values.

3. Sender connects to your server – The sending server attempts delivery to the highest priority (lowest number) server first.

4. Fallback if needed – If the primary server is unavailable, the sender tries the next server in priority order.

Priority Values

Each MX record includes a priority (or preference) value that determines the order in which mail servers are tried:

• Lower numbers = higher priority – A server with priority 10 is tried before one with priority 20.

• Equal priorities = load balancing – Servers with the same priority receive mail in a round-robin fashion.

• Backup servers – Higher priority values (like 50 or 100) designate backup servers used only when primary servers fail.

A typical configuration might have your primary server at priority 10 and a backup at priority 20.

Null MX Records

A null MX record explicitly declares that a domain does not accept email. This is useful for domains that only send mail or exist purely for web services.

The null MX format is a single MX record with priority 0 pointing to "." (a single dot). When other servers see this record, they know not to attempt delivery and can immediately return a bounce message.

Using null MX is better than having no MX records at all, as it provides a clear signal rather than forcing senders to wait for timeouts.

What MailHealth Checks

Our MX checker examines your configuration for:

• Record existence – Confirms MX records are published for your domain.
• Server reachability – Tests whether your mail servers are accessible and responding.
• Priority configuration – Validates that priority values are properly set.
• Null MX detection – Identifies if your domain is configured to reject all mail.
• Common issues – Detects misconfigurations like pointing to IP addresses instead of hostnames.

Properly configured MX records are essential for email deliverability. They ensure that legitimate messages reach your mail servers and provide redundancy when primary servers experience problems.