If your inboxes come pre-warmed from PuzzleInbox do you still need to keep warmup running in Instantly or Smartlead? I ran the test
warmup_overlap_pat · 2026-08-14 · 680 views
This question comes up constantly so I actually ran the test instead of guessing.
20 PuzzleInbox Google Workspace inboxes, split into two groups of 10. Group A: pre-warmed inboxes with Instantly warmup still enabled after delivery. Group B: pre-warmed inboxes with Instantly warmup turned off completely on day one. Same cold email campaigns. 45 days of data.
The result: almost no meaningful difference.
Group A (warmup still running): 3.9 percent average reply rate. Group B (warmup off): 3.8 percent average reply rate. Bounce rates and spam placement scores from GlockApps were essentially identical across both groups throughout the test.
My conclusion: PuzzleInbox inboxes arrive properly warmed. If the warmup was done right before delivery, continuing to run warmup emails through your sending platform does not meaningfully improve deliverability. You are paying for warmup credits and consuming warmup sending volume for no measurable benefit.
Two caveats.
First: this changes if you plan to scale volume aggressively past 20 emails per inbox per day. The warmup history matters more when you push the limits. I kept both groups at 15 emails per day for this test.
Second: if you ever pause a PuzzleInbox inbox for more than two weeks, re-enable warmup before resuming cold sends. Reputation can decay during long idle periods.
The practical takeaway: when you connect a pre-warmed PuzzleInbox inbox to Instantly or Smartlead, you can safely disable the sending platform warmup immediately and start cold email sends right away. No need to wait another two weeks and burn warmup credits on top of what PuzzleInbox already did.
One less thing to manage. One less cost. No deliverability trade-off.