What happens if your MX record is missing?
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.
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