What does MX priority mean?

Senders try the lowest preference number first and fall back to higher numbers if it is unavailable. Equal numbers share load.

Can an MX record point to an IP address or a CNAME?

No. RFC 5321 requires an MX target to be a hostname with A/AAAA records; pointing at an IP or an alias causes delivery failures with some senders.

MX Lookup

An MX (mail exchanger) record is the DNS record that tells other mail servers where to deliver email for a domain. This lookup lists each MX host with its priority and resolved IP addresses and flags hosts that are missing or do not resolve.

When to use this: Mail to a domain is not arriving, or you have just moved email to a new provider. Command prefix mx:

About the MX Lookup

Look up the MX records that tell the internet where to deliver email for a domain. ProbeKit resolves every mail exchanger to its IP addresses and flags missing, duplicate or unresolvable hosts.

FAQ

What does MX priority mean?: Senders try the lowest preference number first and fall back to higher numbers if it is unavailable. Equal numbers share load.
Can an MX record point to an IP address or a CNAME?: No. RFC 5321 requires an MX target to be a hostname with A/AAAA records; pointing at an IP or an alias causes delivery failures with some senders.