Google Workspace versus Outlook 365 for cold email in 2026. Six months of inbox placement data across both providers compared side by side
gws_vs_outlook_carl · 2026-09-09 · 0 views
Six months running a split infrastructure. Half Google Workspace, half Outlook 365 through PuzzleInbox. Same campaigns, same copy, same Smartlead setup. Here's what the placement data showed.
GlockApps scores over six months:
Google Workspace inboxes: average 93 percent inbox placement on Gmail addresses, 87 percent on Outlook addresses.
Outlook 365 inboxes: average 89 percent inbox placement on Outlook addresses, 76 percent on Gmail addresses.
The pattern holds. Each provider has a home-field advantage on its own platform. Google Workspace inboxes perform better hitting Gmail recipients. Outlook 365 inboxes perform better hitting Outlook and Microsoft recipients.
Reply rates followed the same direction. My ICP skews toward companies using Google Workspace themselves. Mid-size SaaS companies have moved heavily toward Google over the past three years. So Google Workspace sending inboxes outperformed Outlook across most campaigns by about 0.7 percentage points in reply rate.
When my ICP shifted to manufacturing and financial services, which are heavier Outlook shops, the Outlook inboxes narrowed that gap to near zero.
The practical conclusion: match your infrastructure to your ICP's email provider. If you're selling to SaaS companies, lean heavier on Google Workspace. If you're selling to enterprise, healthcare, or government, lean heavier on Outlook.
I use PuzzleInbox for both types. They handle DNS and warmup consistently regardless of provider, which makes managing a split infrastructure much simpler than doing it yourself.
One operational difference worth noting: Outlook 365 inboxes need a longer warmup than Google Workspace. Add a week to your standard timeline. Running them at 12 sends per day instead of 15 for the first three months after warmup is also worth the conservative approach. The reply rate difference from sending slightly less is minimal. The domain health difference over six months is not minimal.
If your ICP is mixed, run both. Use Clay to identify the email provider at the company level and route contacts to matching infrastructure. It's a 20-minute Clay workflow build and it's worth every minute at scale.