Real GWS vs Azure tenant vs SMTP. 6 month test across 3 infrastructure types

infra_tester · 2026-05-04 · 2,450 views

Ran cold email on 3 different infrastructure types for 6 months. Same copy, same ICP (B2B SaaS 50-500 employees, VP Marketing), same sending platform (Instantly). Only variable: infrastructure type. Here is the data.

Setup A: Real Google Workspace (PuzzleInbox). 10 pre-warmed GWS inboxes at $3/inbox. Send volume: 15 emails/inbox/day across 6 months.

Setup B: Azure/Entra tenant (Hypertide). 10 Azure tenant inboxes. Similar volume.

Setup C: Private SMTP dedicated IP (Mailreef). 10 inboxes on dedicated IP infrastructure. Same volume.

6-month aggregate results.

Real GWS: 27,000 emails sent. Reply rate 4.3%. Bounce 1.1%. Spam 3.2%. Inbox placement 88%. 243 meetings booked.

Azure/Entra: 27,000 emails sent. Reply rate 3.1%. Bounce 2.2%. Spam 9%. Inbox placement 78%. 175 meetings booked.

Private SMTP: 27,000 emails sent. Reply rate 2.4% (after 4 weeks of warm-up). Bounce 3.1%. Spam 14%. Inbox placement 70%. 129 meetings booked.

The insights.

1) Real GWS dominated Gmail-heavy prospects. Microsoft-heavy prospects (~30% of list) had lower GWS performance.

2) Azure/Entra did better to Outlook prospects specifically. Worse to Gmail.

3) Private SMTP took 4 weeks to reach steady-state. First month was basically wasted.

4) Cost per meeting: Real GWS $2.50. Azure/Entra $4.30. Private SMTP $7.80.

The conclusion. For mixed ICP cold email at this volume (under 50K emails/month), real Google Workspace from PuzzleInbox produces best cost per meeting by a wide margin. Private SMTP requires far more volume to justify the warming investment. Azure/Entra has specific use cases but loses to real GWS at typical volumes.

What I would do differently. For Microsoft-heavy prospects, I would add real MS365 (not Azure/Entra). PuzzleInbox Outlook at $0.35/inbox is the cheapest pre-warmed MS365 option and specifically designed for cold email. That combination (GWS for Gmail prospects + MS365 for Outlook prospects) is the optimal multi-platform cold email stack.