How can split-brain DNS cause email delivery problems?

Authentication inconsistency:

• Internal SPF check passes (internal DNS shows authorized IP)
• External receiver queries public DNS (different result)
• Authentication fails unexpectedly

MX routing confusion:

• Internal MX points to internal server
• External sender cannot reach internal server
• Mail delivery fails or times out

Testing confusion:

• Tests from inside network succeed
• External senders report failures
• Hard to reproduce problems

DKIM verification:

• If DKIM selector resolves differently, signature verification fails
• Keep email authentication records consistent between internal and external DNS.

Conflicting instructions between harbor offices cause delivery to the wrong dock or failed verification.