14 days of warmup is the minimum not the target. Here is what the data actually shows
warmup_watcher_jo · 2026-06-19 · 1,250 views
Everyone says warm up for 14 days. What nobody says is that 14 days is the floor, not the goal.
I've tested warmup durations across about 90 inboxes over two years. Here's what the data actually shows.
14 days of warmup gets your inbox to a baseline. Reply rates in the first campaign are typically 1.5 to 2.5 percentage points lower than what the same inbox produces after 45 days of combined warmup and gradual sending history. The inbox has earned some reputation by day 14, but not enough to carry real cold email volume without taking a hit.
What happens between day 14 and day 45.
Google's reputation signals keep building after warmup starts. Inbox placement at day 14 on GlockApps averages around 82 to 85% in my tests. At day 30 to 45 with gentle sending in the mix, that climbs to 90 to 94%. That 8 to 10 percentage point gap translates directly into reply rate.
What I actually do now.
I use PuzzleInbox pre-warmed inboxes, which arrive with warmup already running. Even with those, I don't put fresh accounts on full cold email volume on day one. I ramp them: 5 cold emails per day in week one, 10 in week two, 15 by week three, and 20 by week four. The inbox builds reputation from real sends gradually instead of jumping straight to full volume.
The cost of impatience.
I've watched operators receive pre-warmed inboxes and blast 20 cold emails per day from day one. Reply rates look fine for two to three weeks, then plummet. Google's algorithms notice the behavior pattern and downgrade delivery. The operators conclude the inboxes are burned. Often the problem is just that they never let the reputation fully develop before stressing it.
Warmup is not a box you check before you start sending. It's a process you maintain in parallel with all your cold sends. Keep warmup active on every inbox, every day, even after your campaigns are live. The ongoing warmup signal tells receiving servers these inboxes have normal email activity, not just cold email blasting.
14 days minimum. 45 days preferred. Warmup never fully off.