Google Postmaster Tools and Microsoft SNDS (Smart Network Data Services) are free dashboards from the two largest mailbox providers that let senders monitor how their email is received. Google Postmaster Tools reports on Gmail traffic — spam rate, domain and IP reputation, authentication results and delivery errors — while Microsoft SNDS shows how Outlook, Hotmail and Live treat a sender IP address, including complaint rates and spam-trap hits.
How they work
Both tools require the sender to prove ownership: a DNS TXT record for Google Postmaster Tools, and IP registration for Microsoft SNDS. Once set up, they surface data straight from the mailbox provider that you cannot see in your own sending logs — the user-reported spam rate at Gmail, or the color-coded complaint bands at Outlook. That makes them the primary way to diagnose deliverability problems at the two providers that dominate most lists.
Why they matter
Google Postmaster Tools and Microsoft SNDS act as early-warning systems for sender reputation. A rising Gmail spam rate or a red SNDS band signals trouble before mail starts getting blocked, so you can pause, clean your list and recover. Mailpro monitors IP reputation across providers for you; read what IP reputation is or see how to improve your deliverability score.
Mailpro and deliverability
Provider-grade deliverability monitoring, built in
Mailpro watches your sending reputation across Gmail, Outlook and every major provider, and routes around problems before they reach the inbox, so you don't have to read a dashboard every morning.