How do I tell if an email domain has valid MX records?

To check whether an email domain has valid MX records, you can query its DNS MX record set.

What to look for

A domain “has valid MX records” if:

• It returns one or more MX records
• Those MX records point to real hostnames that resolve in DNS
• The records have sensible priorities (lower number = higher preference)

Quick ways to check

1) Using dig (Linux/macOS/Windows with tools installed)

dig MX example.com

If MX records exist, you’ll see something like:

example.com.  3600  IN  MX  10 mail.example.com.
example.com.  3600  IN  MX  20 backup.example.com.

2) Using nslookup

nslookup -type=mx example.com

3) Using host

host -t mx example.com

How to interpret results

• MX records present: good sign for mail delivery
• No MX records: many mail systems will fall back to the domain’s A/AAAA record, but that depends on the sender and is not ideal
• MX points to a hostname that doesn’t resolve: invalid/broken setup
• MX points to itself without proper A/AAAA: may still be acceptable in some setups, but the target must resolve

Programmatic check

If you’re writing code, query DNS for MX records and then verify each target hostname has A/AAAA records.

Example logic:

1. Lookup MX for domain
2. If none, domain may still receive mail via A/AAAA fallback
3. For each MX host, ensure it resolves to an IP address

Important note

Having valid MX records does not guarantee the mailbox exists or that the server accepts mail for a specific address—only that the domain is configured to receive email at those mail servers.

If you want, I can also show you how to check this in Python, JavaScript, or with a one-liner in the terminal.