SPF, DKIM, DMARC

SPF, DKIM and DMARC are email authentication mechanisms. SPF states which servers may send mail from your domain, DKIM signs messages digitally, and DMARC says what to do with mail that fails verification.

Set up correctly, they make sure your emails get through (rather than landing in spam) and make it harder for fraudsters to impersonate your company. Their absence is one of the most common causes of business email problems.