I sent 1000 identical cold emails from Google Workspace and Outlook to separate lists with matched ICPs. Here are the deliverability results
gws_outlook_tester · 2026-09-19 · 0 views
Ran a controlled deliverability test over 30 days. Same email copy. Same sequence timing. Same ICP segments matched by company size and industry. One set of 5 inboxes on Google Workspace through PuzzleInbox. One set of 5 Outlook inboxes also from PuzzleInbox. Both fully warmed for 14 days before sends started.
The test setup. 500 emails from Google Workspace inboxes, 500 emails from Outlook inboxes. Both sets used ZeroBounce-verified lists. GlockApps inbox placement test run before launch on both sets. Both passed at 90%+. SPF, DKIM, and DMARC passing on all 10 domains before a single send went out.
Google Workspace results. Reply rate: 3.9%. Bounce rate: 0.8%. Reported spam: 0.1%. Meetings booked: 8.
Outlook results. Reply rate: 3.4%. Bounce rate: 1.1%. Reported spam: 0.2%. Meetings booked: 7.
What the data actually says. The gap is smaller than I expected. Google Workspace came out slightly ahead on every metric but not by a dramatic margin. If you're already on Outlook and your infrastructure is dialed in, you don't need to switch just for marginal deliverability gains. The warmup period and DNS authentication matter more than which platform you're on.
The bigger takeaway. Both sets beat my old shared SMTP inboxes by a factor of roughly 3x on reply rate. Dedicated inboxes with proper authentication destroy shared infrastructure on every metric regardless of whether you pick Google or Microsoft.
Provider choice is a second-order decision. Infrastructure quality is the first-order decision. Get that right before you spend time debating Google vs Outlook.