Glossary
DMARC (DMARC)
An email policy that ties SPF and DKIM together and tells receiving providers what to do when a message fails those checks.
DMARC stands for Domain-based Message Authentication, Reporting and Conformance. That is a mouthful, so here is the plain version. DMARC is the rule that ties your other two email settings together and tells receiving providers what to do when an email claiming to be from you fails their checks.
SPF and DKIM each answer a question. SPF asks whether the sending server is approved. DKIM asks whether the message is genuine and unaltered. DMARC sits on top and says: if those checks fail, here is how to handle it.
SPF check + DKIM check
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DMARC decides: do nothing, send to spam, or reject
You choose the policy. It can start gentle, just watching and reporting, then tighten to send failing mail to spam or reject it outright. That way, if a scammer tries to send email pretending to be your domain, providers know to block it.
Why this matters for making money online: DMARC protects your sending reputation, and reputation is what keeps your real emails landing in inboxes. It also stops others from impersonating your brand, which protects the trust you are trying to build. As a bonus, many major providers now expect senders to have DMARC in place at all.
You do not build this from scratch. Your email service provider gives you the record and guidance. To see how email fits a real business, read how email marketing makes money.