What happens when a DNS record is misconfigured?

DNS misconfigurations cause various email problems:

Missing MX record: Senders cannot find your mail server. Inbound mail bounces.

Wrong MX target: Mail routes to the wrong server. Messages may disappear or be rejected.

SPF syntax error: Authentication fails. Messages may spam or be rejected.

DKIM record missing: Signatures cannot be verified. Authentication fails.

DMARC misconfigured: Policies applied incorrectly or reports not delivered.

PTR mismatch: Reverse DNS check fails. Some servers reject mail.

DNS errors can be invisible for days until someone reports missing mail or you check authentication results.

Wrong coordinates on the navigation chart send ships to the wrong port or into the rocks.