How do new IPs gain trust?

You've got a brand new IP address. Mailbox providers have zero history on it, which means they're watching your first sends very closely. Send too much too fast and you'll hit spam folders, deferrals, or worse. Send smart from day one and you'll build a reputation that holds.

Here's what actually happens during a warmup and what numbers to aim for.

The week-by-week picture

These are rough benchmarks for a B2C marketing sender. Transactional senders can sometimes move faster because engagement tends to be higher. Adjust based on what you're seeing in your metrics.

• Week 1: 200 to 500 emails per day. Your best subscribers only. Think recent openers and clickers from the last 30 days.
• Week 2: 1,000 to 2,000 per day. Add engaged subscribers from the last 60 days.
• Week 3: 5,000 to 10,000 per day. Widen to 90-day openers.
• Week 4: 15,000 to 25,000 per day. You can start including less-engaged segments here, but watch the metrics tightly.
• Weeks 5 to 8: Scale toward your full sending volume in steady increments, roughly doubling every 5 to 7 days if everything looks healthy.

These numbers assume your list is clean and permission is recent. If you're warming up for cold outreach, a purchased list, or a very old list, the math changes significantly (and honestly, so does the risk).

The signals that tell you if you're moving too fast

Gmail and Outlook will give you feedback through delivery patterns before they give you a hard block. Watch for these:

• Complaint rate: Keep this below 0.08% at all times. Above 0.1% and Google starts routing your mail to spam. Above 0.3% is a serious problem. If you have access to Google Postmaster Tools, check it daily during warmup.
• Bounce rate: Hard bounces above 2% signal a dirty list, and a dirty list on a new IP is a fast way to kill your reputation before it starts. Clean before you warm.
• Deferral rates: Temporary failures (4xx responses) mean the receiving server isn't ready to accept your volume yet. High deferrals are a signal to slow down, not push through.
• Open rates: A significant drop during warmup often means deliverability has dipped. Watch for week-over-week changes rather than absolute benchmarks, which vary by industry.

What builds trust, specifically

Mailbox providers score your new IP on a mix of signals that go beyond just volume. Authentication is the baseline. Every single message from day one needs to pass SPF, DKIM, and DMARC, no exceptions. Failures on a new IP look especially bad because you have no positive history to offset them.

Engagement is the accelerator. When your first sends produce strong open and click rates, providers start treating subsequent sends more favorably. That's exactly why you start with your most engaged subscribers. You're essentially giving the IP its first reference letters.

Consistency matters too. Sending a spike of 50,000 on day three after barely 500 on days one and two is a red flag. Erratic volume patterns look automated and untrustworthy. Slow and steady actually wins this race.

A note on shared vs. dedicated IPs

If you're on a shared IP, you skip most of this. The warmup has already been done by the ESP managing that pool. Dedicated IPs are where warmup matters, typically for senders hitting 50,000 or more emails per month. Below that volume, a shared IP with a reputable ESP is usually the better choice anyway.

But if you're not sure whether your current setup is building or burning reputation, our free blocklist checker is a good first stop. Or if warmup is actively going sideways, our SOS hotline is free and we actually pick up.