Email was built without a check on the sender's address, so anyone can type yours into the From line. Authentication cannot stop that, but it lets receivers notice.
A sender can write any address in the visible From line. The message then looks like it came from you, even though it did not. The From line is like the return address on a postcard: it says whatever the sender writes.
SPF shows whether the sending server is allowed to send for your domain. DKIM shows whether the message was signed by your domain.
DMARC connects those results to the address people see and tells receivers what you want done with failures. It also asks for reports.
Authentication helps receivers, but it does not delete the message everywhere. Look-alike domains, with slightly different spelling, are outside its reach.
Our free Website check looks at SPF, DKIM and DMARC for your domain and reports what is in place. Open Website check
Last reviewed: 2026-11-02
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This page gives general information and is not legal, financial or medical advice. [email protected]