What happens if your MX record is missing?

Question

Review My Emails · Accepted Answer

Missing MX records cause delivery problems:

Fallback behavior: Some senders try the A record as a last resort (RFC 5321 allows this). But many do not.

Likely outcome: Most mail bounces with errors about no mail exchanger found.

Delayed discovery: You might not notice for hours or days until someone reports missing mail.

Authentication interaction: Even if A record delivery works, authentication may fail if SPF does not account for this path.

Always have properly configured MX records. Do not rely on A record fallback.

A port with no docking assignments leaves ships circling the harbor or returning to origin.