What is IP warm up and why is it important?

Written by Will Chidlow on 8th October 2015

(Last updated 10th May 2018)

What is IP warm up and why is it important?

Most people understand the benefits that good email marketing can have for their business but making it happen can be a difficult process to grasp. One area that often causes confusion is IP warming. Heres our quick guide to what it is and when it’s used.

Have you ever wondered why certain emails end up in your junk/spam folder whilst others make it into your inbox? A lot of this depends on the reputation of the IP address that was responsible for sending the email in the first place. Internet Service Providers (ISPs) gather data on all IP addresses and rank them depending on how trustworthy they are, think of it like the IP address equivalent of your credit score. If an IP address sends out a large amount of emails without first establishing a good reputation with ISPs then it’s likely that the email will be sent to the junk folder.

What is it?

Warming an IP address is the name given to the process that is used to build a good reputation for your IP address. The process involves sending regular but small email campaigns over a period of time and gradually increasing the volume of emails as ISPs begin to form a positive reputation for your IP address. Once a solid reputation has been gained, you will be able to send out much larger and more regular email campaigns from your IP without ISPs getting in the way.

Do I need it?

Whether or not you need to warm your IP address depends on several factors:

Dedicated IP address

IP warming is only needed if you are using your own dedicated IP address to send out email campaigns. Email marketing services such as Campaign Monitor or Mailchimp often send your emails along with many other service users emails from their own IP addresses. If you are using a service like this then you will not need to warm the IP address. This means that the delivery rate of your campaigns is dependent on the reputation of the shared IP address and this could be beneficial or detrimental depending on the previous campaigns and reputation of the IP. If you are using a shared IP address currently and sending high volumes of emails then it might be worth looking at setting up your own dedicated IP address, doing so has the potential to increase your campaigns delivery rate.  

Large volume of emails

If you’re sending less than 10,000 emails per month then it is unlikely that ISPs will be concerned with your sending activity and therefore IP warming isn’t necessary.

The process

To warm up an IP address, send low volume email campaigns over a period of time to start gaining the trust of the ISPs. As time progresses slowly increase the volumes you are sending. This helps ensure your emails reach their recipients without delay or even worse deletion. A simple way of calculating a warm up schedule is to work out how many emails you want to send eventually, half it, and divide it by 30. This will give you a daily email volume to aim for over month 1 of your warm up process. For month 2 you can simply double your email volume. here is an example based on an eventual monthly send of 120,000 emails:


Week 1

2000 emails per day

Week 2

2000 emails per day

Week 3

2000 emails per day

Week 4

2000 emails per day

Week 5

4000 emails per day

Week 6

4000 emails per day

Week 7

4000 emails per day

Week 8

4000 emails per day

As the warm up process continues you can increase both the number of campaigns you are sending as well as the number of recipients you are sending each campaign to. It is important not to rush this process as an IP address with a bad reputation can be very difficult to improve.

When warming up an IP address you should also carefully consider your data sources and do your best to ensure that your recipients are genuine subscribers with valid email addresses. Emails flagged by the reader as junk or un-subscribers will adversely affect your positive efforts.


IP warming isn’t for everybody but hopefully this post has helped you work out if it is something you should be doing when setting up new email marketing platforms. A similar approach can also be used when wanting to ramp up the volume of emails you are sending in a way that won’t impact delivery rates. Email marketing can be such a powerful way to interact with your customers so ensuring your emails reach their recipients is as important as the content itself.

If you have taken a different approach to warming an IP then we would love to hear about your approach, equally if you have questions about our approach then please feel free to comment.

by Will Chidlow