Level: Advanced
Many organizations send from several different email service providers or systems simultaneously, and coordinating authentication across all of them correctly requires deliberate technical planning.
Every Sending Source Needs Its Own DKIM Configuration
Each distinct sending platform needs its own properly configured DKIM key and selector, since a single DKIM setup typically can't be shared cleanly across genuinely separate systems.
SPF Needs to Include Every Legitimate Source
The domain's SPF record must include or authorize every platform actually sending mail on the domain's behalf, which is a common point of failure as new tools get added without updating SPF.
Keep a Master Inventory of Every Authorized Sending Source
Maintaining a current, documented list of every system authorized to send as your domain makes it far easier to keep SPF and DKIM configuration accurate as your sending stack evolves.
Next step: Use the Find DNS Records to check your current SPF and DKIM records against a full inventory of every system actually sending mail on your domain's behalf.