What are SNDS and Postmaster APIs used for?

SNDS (Smart Network Data Services) from Microsoft and Postmaster APIs from Gmail provide MBP-side reputation data directly from the source. They show how these major providers view your sending reputation.

SNDS shows: IP reputation status, spam complaint rates, trap hits, and filter results for email to Microsoft properties. It's the authoritative view of your standing with Outlook, Hotmail, and related services.

Gmail Postmaster Tools shows: domain and IP reputation, spam rates, authentication success, delivery errors, and encryption status. For Gmail, which often represents significant list portions, this data is essential for understanding delivery.