Gmail and Outlook use different filtering algorithms and reputation databases. Gmail weighs DMARC alignment and sender reputation heavily. Check Google Postmaster Tools (postmaster.google.com) — it shows your domain’s reputation score and spam rate as seen by Gmail. A score below ‘High’ means Gmail is applying extra scrutiny. Fix: ensure DMARC p=reject is set, DKIM is signed from your domain, and your list engagement rates are high.
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