IP warming

New sending IPsStands for "Internet Protocol". The IP address is assigned to one or more devices that are connected to a network. The IP address serves as a unique identifier of the device. have no sending history and are considered a cold IP. At this point, they need to acquire a good reputation with ISPsStands for "internet service provider".

Hotmail, Yahoo!, AOL, Gmail need to see that you are sending important, consent-based messages to permit your mailings into your recipient's inbox.

IP warming is the process used to build a good reputation with ISPs. ISPs monitor your IP to track your sending behavior and are likely to accept your messages based on a good sending reputation.

The IP warming process includes sending consistent, low volume email campaigns, gradually increasing this volume over time until you reach your full volume capacity. ISPs then gain confidence in you as a sender.

It can take 4-6 weeks to complete the IP warming phase. This depends on your volume amount and how well your recipients engage with your messaging.

During the warming process, ISPs set receiving limits on your IP until you meet their standards of good reputation.

Image:  IP Warm Up and Reputation

Getting started with IP warming

IP warming schedule

Following an IP warming schedule assists in gradually establishing a reputation with ISPs as a legitimate email sender. Start with small email volumes, and gradually increase volume each day according to the two-week set schedule. The following schedule suggests a maximum of 40 percent to 100 percentage increase in volume per day. This however greatly depends on factors including list hygiene, how engaged your recipients are, and spam complaints among other things.

Image: Example IP warming schedule

Day Daily sending volume
1 500
2 1000
3 2500
4 5000


6 20000
7 40000
8 60000
9 100000
10 150000
11 200000
12 250000
13 300000
14 400000
  Continue to double your volume until you have reached your target daily volume.

Tips during the IP warming process

What can cause delivery issues during IP warming

What ISPs like to see

  • Consistent opens and clicks
  • Consistent email frequency
  • Email best practices are in place, as detailed in Deliverability best practices.
  • Emails are authenticated (SPF, DKIM, DMARC)

Warming a sending domain

A sending domain requires a good sending reputation for messages to enter your recipients’ inboxes. Domain warming is similar to IP warming, as it represents mailing practices and volume. The same warming approach mentioned above can be applied to warming up sender domains. The difference however is that domain warming focuses on recipient engagement, which is the key factor to focus on.