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When a business starts doing email marketing and sends email campaigns, inbox providers (like Gmail, Outlook, etc.) create a “reputation profile” of that sender. Each inbox provider has its own reputation profile.

The better reputation, the more emails will avoid ending up in the SPAM folder. Just like your real-life reputation, your email reputation can’t be created in just one day.

It requires time and effort—and a plan.

This is where IP warming comes in.

What is IP warming?

IP warming, IP warm-up or reputation warmup is a process of improving your “reputation profile” so that you avoid the SPAM folder. You do this by gradually increasing the number of emails you send out based on a very specific schedule.

IP warming is highly recommended if your subscriber list is higher than 50,000 contacts.

This procedure is normally performedy done when:

  • you’ve just move from one email marketing service to another one, thereby gaining a new dedicated IP address
  • you’ve just started with email marketing

It’s also important that the subscribers in your first few rounds are pretty active.

This means that they’ll be more likely to open your emails and click them, which sends a good signal to Gmail and other providers that your content is quality and your IP address can be trusted.

So, let’s dive into how you can positively affect your reputation with IP warming.

What affects reputation?

There are a few important things that can affect your sender’s reputation.

Let’s look at the positive and negative factors.

Positive factors that increase your reputation profile

These are the factors you should be aiming for:

#1 Highly engaged list, with a high click rate

The threshold here for “high click rate” will depend on the industry you’re in. That’s why subscriber segmentation will be your best friend.

#2 The email is wanted

This means that the subscriber explicitly agreed to receive an email. That’s why lists must be opt-in and preferably GDPR-compliant.

#3 Gradually increasing sending volume

If you have 500,000 emails in a list, starting your email marketing by sending campaigns to all of them immediately is a really bad idea.

You need to start small (say, 10,000 emails on day 1), and then gradually increase by 10-20% per day.

If you start sending large batches on day one, inbox providers might see this as a threat and a spam attack. Therefore, your email will automatically be marked as spam.

#4 A clean list

If someone hasn’t interacted (clicked on your emails) in the last 12 months, that contact should be treated as inactive.

Such emails might later become spam traps. If a trap receives emails, this tells inbox providers that the sender isn’t following email marketing best practices.

As a result, your reputation suffers.

Pro tip: when you migrate from one email marketing platform to another, at first migrate your best contacts who are constantly opening and clicking your emails and start sending to them only.

That way you’ll gradually transfer your “reputation” from one email marketing platform to another.

After a while, you can migrate the rest of the mailing list.

Once again, migrate gradually. Start with small list, then grow the number of contacts.

Negative factors that can damage your reputation profile:

These are the factors you definitely need to avoid as much as you can:

#1 A high complaint rate

If the email is unwanted, people will mark the emails as spam. This is one of the primary factors which lower the sender’s reputation. In the end result, all your emails might start landing in the SPAM folder. Therefore, try to avoid spam complaints as much as possible.

#2 A high bounce rate

This usually means that the list is outdated, low quality, or purchased. Inbox providers treat such senders poorly and affect their reputation.

#3 Low engagement

If a subscriber received 50 emails but did not open any, this is just another signal to the inbox provider that the sender is not following best practices. Therefore, more and more of his/her emails will be placed into the spam folder.

Saying “goodbye” to inactive contacts is always a good thing.

We’ve seen multiple times when a smaller active list of 10,000 contacts drives much more sales than 50,000 (because 40,000 contacts were inactive and those bad contacts were damaging the sender’s reputation).

#4 Too frequent campaigns

Even high-quality subscribers might be overwhelmed by receiving too many campaigns a day and will mark your emails as spam.

The ideal frequency is 2-3 times/week. For daily senders: no more than once a day (with rare exceptions when there is a super rare once-in-a-quarter sale, etc.).

#5 A sudden increase in the number of emails sent

If a sender is usually sending to 50,000 subscribers and then starts sending to 150,000, this spike will cause more emails to be sent to the spam folder (because inbox providers consider spikes as an unexpected behavior and spam attack).

If you want to increase your mailing list size, do that gradually. Add 10,000 (or fewer) contacts with every delivered campaign.

#6 Constantly switching between different email service providers

This hurts your sender reputation because the inbox provider might start seeing the sender as a spammer who’s trying to hide his/her trail.

How to get started with IP warming

IP warming is a process by which a sender is gradually increases the volume of emails sent.

This is crucial for successful email marketing and especially important when:

  • a business has just started doing email marketing
  • a business is switching between email service providers

Gradually increasing your email volume helps you build a good and strong email sender’s reputation. If you have more than 50,000 contacts, then you should definitely follow these IP warming best practices.

These are the best and worst approaches you can take in your IP warming strategy.

The bad approach

If you want to ruin your reputation profile, you would export all emails from the old marketing platform, import them to the new one and start sending mass emails to them all at once.

Even worse approach: Also export the bounced/unsubscribed contacts from the old email marketing platform and try sending emails to them with the new platform.

Expected result: a ruined sender reputation and the majority of emails will land in the spam folder.

The good approach

Now, for what you actually should be doing.

  1. Export only those contacts who have clicked on your emails within last 3 months, plus any new subscribers.
  2. Import them to the new email marketing platform and start sending emails to them.
  3. Then, you can start to gradually add more contacts (say, in addition add those who have clicked in the last 6 months).
  4. It’s recommended to increase the list in the new email marketing platform by at least 10-20% with every campaign.

It’s also a good practice to segment out those contacts that haven’t opened a campaign in the last 12 months.

Then, do not import them to the new email marketing platform, at all. They will just damage your sender’s reputation on the new platform.

During this warmup period the sender will be using two email marketing platforms:

  • The new platform – for the most engaged customers. The number of subscribers will steadily be increasing
  • The old platform – for the rest of contacts. The number will be gradually decreasing.

Here’s a sample IP warming schedule for a client if he/she has 50,000 recipients in total:

IP warming schedule for a business with 50,000 contacts in total

For 300,000 contacts, it’s pretty much similar in concept:

IP warming schedule for a business with 300,000 contacts in total

When Omnisend client Chellysun switched from Recart to Omnisend, they used the following IP warming schedule to help improve their deliverability and ensure they stay out of the spam box.

The number of emails sent by Chellysun over time using the IP warming technique

As you can see, they didn’t follow the recommended schedule perfectly, so that the difference between the 9th campaign and 10th campaign was more than 80,000 contacts.

Nonetheless, by the 10th campaign (after carefully segmenting subscribers for the first 9 campaigns), their reputation profile had already increased.

You can read about how Chellysun used IP warming here.

So, what happens if a marketer doesn’t use IP warming?

Again, IP warming is a crucial tactic if two conditions are met:

  • you have more than 50,000 contacts
  • you are either starting email marketing, or you’re switching to a new email marketing platform

If those conditions are true for you and you don’t use IP warming, the result is obvious:

Your sender reputation will go down.

More and more of your emails will automatically be sent to the Spam folder.

Your open rates will decrease.

Your sales will decrease.

In total, your whole email marketing and marketing automation strategy will be a failure.

However, if you use it:

  • your reputation improves
  • open rates (and sales) increase
  • your email marketing and marketing automation succeed
  • your business flourises

So, there’s really no good reason not to do it.

Click here to see how Omnisend customer Chellysun used IP warming successfully.