Check MX, SPF and DMARC DNS records for any domain — verify your mail servers are set up correctly.
MX (Mail Exchanger) is a DNS record that specifies the mail servers responsible for accepting emails for a domain. SPF (Sender Policy Framework) is a TXT record that lists authorized sending IP addresses. DMARC (Domain-based Message Authentication) defines the policy for handling emails that fail SPF or DKIM checks.