Mistake: flying blind without Google Postmaster Tools

Mistake: flying blind without Google Postmaster Tools
Operators obsess over their sending tool's 'health score' — a made-up number — while ignoring Google Postmaster, which shows the actual spam rate Google assigns your domain. You find out you're flagged only when replies hit zero.

The fix: verify each sending domain in Postmaster Tools, watch the Spam Rate dashboard, and pause any domain that crosses 0.10%. Microsoft's SNDS does the equivalent for Outlook. No sending tool gives you this; it's source-of-truth.

Pros / Cons of Postmaster monitoring:
— Pro: real spam-complaint data straight from the mailbox provider
— Pro: early warning days before reply rate collapses
— Con: needs enough daily volume to populate (low-volume domains show nothing)
— Con: Google-only; you still need SNDS for Outlook

Verdict: 5/5. Non-negotiable and free.

Who it's for: every cold sender past trivial volume.