Add every system that is allowed to send email using your domain:

1. If you send through Microsoft 365, add spf.protection.outlook.com as an include domain.
2. If you send through Google Workspace, add _spf.google.com as an include domain.
3. If an on-premises Exchange server sends mail directly, add the public IPv4 address used for outbound email.
4. If a website, CRM, help desk, newsletter platform or other service sends mail for your domain, add the SPF include domain or sending IP provided by that service.

Only authorize services that actually send email for your domain. Check each provider's current SPF documentation before publishing.