I tracked cold email inbox warmup scores daily for 30 days across three providers. This is how many days you actually need before sending a real campaign
warmup_days_felix · 2026-09-03 · 0 views
Warmup tool sellers say 14 days is enough. I wanted actual data. I tracked GlockApps inbox placement scores daily for 30 days across inboxes from three different providers, then sent a cold campaign test at the end of each week to see what real inbox placement looked like at each stage.
Provider A: PuzzleInbox pre-warmed Google Workspace inboxes.
Day 1 GlockApps score: 82 percent inbox placement on cold sends. Day 7: 89 percent. Day 14: 94 percent. Day 21: 96 percent. Day 30: 97 percent.
By day 14, placement was already high enough to run a real campaign. I was confident at day 14. By day 21 there was no meaningful improvement worth waiting for.
Provider B: Budget SMTP reseller inboxes I set up myself.
Day 1: 47 percent inbox placement. Day 7: 58 percent. Day 14: 61 percent. Day 21: 67 percent. Day 30: 71 percent.
Never crossed 75 percent in 30 days. I would not send a real campaign from these inboxes at any point during the test window.
Provider C: A mid-tier Google Workspace reseller.
Day 1: 74 percent. Day 14: 84 percent. Day 21: 88 percent. Day 30: 91 percent.
Acceptable by day 21. Not comfortable until day 28.
The conclusion is obvious. Pre-warmed inboxes from a provider like PuzzleInbox start the warmup phase from a much better baseline. The 14-day rule works if your starting position is already good. If you are starting from a cold SMTP inbox with no reputation, 14 days will not get you to acceptable inbox placement.
My actual recommendation: check your GlockApps score on day 10. If inbox placement is above 90 percent, you can consider a small campaign test. If it is below 85 percent, keep warming. Do not go by calendar days alone. Go by placement scores.