Warming Up An Email List: A Foolproof Guide

If you're sending to a large email list for the first time after switching your email marketing provider, sending domain, or after taking a long break — this can cause temporary deliverability issues. The solution to this is email list warm up or "list warming."

NOTE: This guide only applies to people with opted-in lists. Do not cold email people in bulk, as there is no reliable way to "warm up" a list that was never warm to start.

What is email list warm up?

Email list warm up or "warming" is a way to build a good sender reputation on new email infrastructure or an email list you haven't contacted in a while. By focusing on the most engaged subscribers, and gradually increasing email sending volume, you can establish yourself as a reputable sender to the algorithms.

Who should do email list warm up?

List warming isn't neccesary for everyone, especially smaller senders or folks just starting out. We recommend it only if sending to a list that exceeds 10,000+ people after one of these events has occurred:

• You switched to a new ESP (like Audienceful)
• You changed your sending domain name
• Your email list has been dormant (no sends) for more than 6 months

In all of the above cases, your short-term deliverability will definitely benefit from some level of warming process.

How to do warming successfully

The first thing you'll want to do is find out how to export audience segments as CSVs from your current platform. And then use a tool like Excel or Google Sheets to slice/merge the CSVs together.

Then you'll want to come up with a plan and cadence sending emails to your most engaged subscribers first, before adding in the lesser-engaged folks on later sends. Here's an example plan:

• First, export & send only to subscribers who clicked a link in your last email.
• Then, export & send to subscribers who opened (but didn't click) that last email
• Finally, export & send to subscribers who didn't open or click your last send

You can break this up even futher (eg. subscribers who open more than 75% of the time vs. 50% of the time, etc.) if your list is in the hundreds of thousands or millions.

What is the ideal time to wait between sends?

There's no set rules around how to do list warming or "warm up." Inbox providers don't share any info on how their algorithms work to avoid spammers gaming their systems.

It all depends on your risk tolerance and how much you value the integrity of your deliverability metrics (especially in the short term).

That said, you'll definitely want to break up your sends to each chunk by at least 24hrs.

Stale list? Start with cleaning via an email list verifier

If you haven't contacted the list in a while, it's highly recommended you start by running your list through an email list verifier. This will weed out invalid emails (from domains that have expired, job switchers, etc.) and remove some of the inevitable list rot.

A few good options are the Hunter Bulk Verifier and Neverbounce, however there's hundreds of these services and most will do an okay job when it comes to invalid emails.

Now would also be a good time to look at folks who have never opened an email from you and remove or "clean" them from your list.