Protecting your sending reputation

Outbound mail is checked as well as inbound, which is less common than it sounds and is what stops one compromised account ruining delivery for everyone else on the platform.

Your side of that is mostly the DNS records. With SPF, DKIM and DMARC published and aligned — which they are, once a domain verifies — receivers have everything they need to trust mail from you.

The rest is behavioural: send to people who expect it, keep list sizes sane, and do not send bulk marketing from a mailbox that also sends personal replies. Reputation attaches to the domain, and a domain that does both gets judged on the worse half.