What happens if you skip authentication?

Skipping email authentication creates immediate, predictable problems.

Without SPF:

Receivers cannot verify you authorized the sending IP

Messages fail SPF checks that legitimate mail passes

Higher spam filtering probability

Without DKIM:

Messages lack cryptographic proof of origin

Content integrity cannot be verified

DMARC alignment becomes impossible

Without DMARC:

No policy tells receivers how to handle failures

No visibility into authentication results

Domain is more vulnerable to spoofing

Combined effect: Major mailbox providers like Gmail and Microsoft require authentication for bulk senders. The 2024 sender requirements made this explicit. Unauthenticated messages face aggressive filtering or outright rejection.

For cold email, where you already lack relationship trust, failing technical trust checks guarantees poor deliverability. Arriving without papers means the harbor master doesn't even look at your cargo before turning you away.