IP Warm-Up

IP warm-up is the gradual ramp-up of sending volume on an IP address or domain with no history. Mailbox providers treat unknown senders cautiously, so a slow, steady increase lets them observe good behaviour first.

Why it matters

A new IP that suddenly sends hundreds of thousands of messages looks like a hijacked server or a spammer, and it is likely to be throttled or sent to spam. Warm-up builds a positive sender reputation. It matters when you move to a dedicated IP, change providers or restart after a long pause. Shared IPs from a reputable provider are usually already warm, which is one reason small senders use them.

Example

A sample schedule (illustrative, not a rule):

1. Days 1-3: 200 per day to your most engaged subscribers.
2. Days 4-7: 500, then 1,000 per day.
3. Weeks 2-3: double every few days while watching bounces and complaints.
4. Week 4+: approach full volume.

If deferrals (4xx) or complaints rise, hold or step back rather than pushing on.

Common mistakes

• Starting with the entire list at once.
• Warming with unengaged or old addresses, which produce bounces and complaints.
• Pausing for weeks mid-way, then resuming at high volume.

Related

• Sender Reputation
• List Hygiene
• DNSBL
• Bulk Email
• Tool: Blacklist checker

This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.