How do I monitor progress during warmup?

You've started your warmup, you're sending to your best subscribers, and now you're staring at your dashboard wondering: is this going well? Here's how to actually read what you're seeing, and what to do when the numbers start looking wrong.

Check these every day

During warmup, daily monitoring isn't paranoia. It's how you catch problems before they turn into reputation damage. These are the three numbers that matter most.

Bounce rate should stay below 2%. If you're sending to a segmented list of your most engaged subscribers, you should see this sit well under 1% in the early days. Anything creeping toward 2% is a warning, not a threshold to hit.

Complaint rate should stay below 0.1%. This is the number mailbox providers use to judge whether your recipients actually want your mail. Google starts paying close attention at 0.08%. If you hit 0.3%, you need to stop and diagnose before sending another batch. (A complaint rate that high, that early, usually means your list quality is the problem, not your infrastructure.)

Open rate isn't a pass/fail signal on its own, but it tells you a lot about trajectory. Since you're warming up with your most engaged subscribers, your open rates should be strong. If you see them falling week over week while complaint rates stay low, your warmup pace might be moving faster than your reputation can support.

Set up postmaster tools on day one

Gmail Postmaster Tools shows you domain reputation, IP reputation, spam rate, and delivery errors, all from Google's perspective. It's free. If you haven't set it up yet, do it now. You won't see data until you're actually sending volume to Gmail addresses, so the sooner you activate it, the sooner it starts populating.

Microsoft's SNDS (Smart Network Data Services) does the same job for Outlook and Hotmail recipients. Log in daily during warmup and look for green status across your IP ranges. Yellow means watch carefully. Red means pause everything and investigate.

Watch for these warning signs

Any one of these means you slow down or stop:

• Bounce rate exceeds 2%
• Complaint rate exceeds 0.1% (don't wait for 0.3% to act)
• Gmail Postmaster reputation drops to Low or Bad
• SNDS shows red status on your IPs
• Your domain or IP appears on a blocklist

Appearing on a major blocklist like Spamhaus during warmup is a clear signal you've moved too fast or sent to the wrong people. Don't just remove yourself and keep going. Find the root cause first.

What success actually looks like

You're on track when bounce rates stay low, complaint rates stay below 0.08%, Gmail Postmaster shows Good or High reputation, and open rates are stable or improving as you scale volume. The trajectory matters as much as the individual number. A complaint rate holding steady at 0.05% as you double your daily send volume is a better sign than a rate of 0.03% that's been slowly climbing for a week.

Write your numbers down every day, even just in a spreadsheet. It sounds tedious, but when something breaks in week three, you'll want to see exactly when the trend started.

If you want to check whether your domain reputation is already showing signals before you even start ramping, our free blocklist checker gives you a quick read. And if the numbers you're seeing don't match any normal pattern, our SOS hotline is free and we actually help you diagnose it.