Pre warmed vs standard inboxes. 90 day deliverability tracking across 100 accounts

90day_tracker · 2026-04-10 · 3,340 views

I've been tracking deliverability data for a while and this is the most controlled test I've run. 100 Google Workspace inboxes total. 50 pre-warmed from PuzzleInbox. 50 standard (purchased from the same type of provider, then warmed myself using Instantly warmup). Same domains, same DNS configuration quality, same sending platform, same copy.

I ran GlockApps inbox placement tests on a sample of 10 accounts from each group every 2 weeks for 90 days. Here are the results:

Day 1 (delivery day): Pre-warmed: 86% inbox placement. Standard: 34% inbox placement. The standard accounts had zero sending history, so this is expected. They hadn't been warmed yet.

Day 14 (standard warmup complete): Pre-warmed: 88% inbox placement. Standard: 71% inbox placement. The standard accounts improved dramatically but were still 17 points behind pre-warmed.

Day 30: Pre-warmed: 87% inbox placement. Standard: 79% inbox placement. The gap closed to 8 points. Standard accounts were settling into their reputation.

Day 60: Pre-warmed: 86% inbox placement. Standard: 77% inbox placement. Interesting: standard accounts actually dropped slightly from day 30. Some accounts in the standard group showed inconsistent performance.

Day 90: Pre-warmed: 85% inbox placement. Standard: 76% inbox placement. The gap stabilized at about 9 points. Pre-warmed accounts maintained higher and more consistent placement throughout the entire 90 day period.

Key findings:

• Pre-warmed inboxes never dropped below 83% placement at any testing point.
• Standard inboxes never caught up to pre-warmed. The gap narrowed but never closed.
• Variance was much higher in the standard group. Some standard accounts hit 84%, others sat at 68%. Pre-warmed accounts clustered tightly between 83% and 91%.
• The first 14 days are where pre-warmed accounts deliver the most value. During this period, standard accounts are essentially unusable for cold email while pre-warmed accounts are generating pipeline.

The revenue impact of that 14 day head start is significant. At 50 inboxes sending 15 emails per day, pre-warmed accounts generate roughly 750 emails daily from day 1. Over 14 days, that's 10,500 emails that standard accounts simply can't send. At 87% placement and 4% reply rate, that's approximately 365 replies and 180 meetings that pre-warmed accounts generate before standard accounts even start sending. If you're paying for inboxes, paying a bit more for pre-warmed is paying for 2 weeks of pipeline you'd otherwise miss.