IP address warmup

Warming up an IP address

Before contacting large amounts of customers and in order to keep doing so frequently without hiccups, it is important to proceed to an IP warmup. You also need to warmup your IP if you have had a significant break in email sending.

Warming up your IP allows you to gradually send more emails over your new IP to establish a good sender reputation.

IP warming is the practice of gradually increasing the volume of mail sent with a dedicated IP address according to a predetermined schedule. This gradual process helps to establish a reputation with ISPs (Internet Service Providers) as a legitimate email sender.

When an ISP observes email suddenly coming from a new or "cold" IP address, they will take notice and immediately begin evaluating the traffic coming from that IP. Since ISPs treat email volume as a key determining factor when detecting spam, it is best to begin sending a low to moderate volume, eventually working your way up to larger volumes. This gives the receiving email providers a chance to closely observe your sending habits and record how your recipients engage with your email.

The recipients engagement is the other big factor, together with volume. You could send emails one at a time over several months, but if your recipients are not opening them and deleting or reporting them as spam, your reputation will not improve. It is therefore crucial to actually monitor the results of each sending and only move on to the next if the open and click rates are satisfying.

As a rule of thumb, an open rate in the double-digits and click rate above 1% is satisfying enough to schedule the next sending.

A gradual warmup does not always guarantee a perfect sending reputation. It is still important to follow sending best practices.

The routine

To warmup your IP, you need to gradually send more and more email over your IP address at the rate suggested below. When sending through a new domain and IP address, you are inherently more susceptible for receiving blocks, deferrals, and other reputation-related email errors because recipient servers do not recognize your mail.

It's important to build this reputation over time, which is why we recommend the throttling via IP warm-up as soon as you receive your new dedicated IP. This is a manual process and would require that you segment your sending by breaking up contacts into smaller lists and scheduling your campaigns, as a suggestion.

The goal with IP warm-up is to avoid and/or mitigate deliverability issues that come with lack of reputation such as blocks, deferrals, or bounces.

This chart will give you the recommended schedule. Please note that this schedule assumes the content is relevant to the recipients, it complies with the best practices for email marketing and you are closely monitoring the statistics and each sending has reached acceptable levels before moving on to the next.

This schedule is only a suggestion and should be modified if the open and click rates are poor.

Day Daily volume Day Daily volume
0 50 6 5 000
1 100 7 10 000
2 200 8 20 000
3 500 9 50 000
4 1 000 10 100 000
5 2 000    

When sending more than a thousand emails at a time, it is best to use email throttling to put a delay between chunks of 1 000 emails. One minute of delay should be enough to give more time for even the smaller IPSs to handle the incoming traffic.

If you have any questions or concerns, please contact Custobar support.