What the Heck is IP Warming? (& Why You Really Should Care) >

IPWarming_cropOkay! You’ve spent the last three weeks ideating, creating mock-ups and identifying the perfect audience segmentation. You’ve built the email creative…and tested to ensure that the best email ever devised looks pristine from Lotus Notes 2 through the Gmail app. You send the email and wait 24 hours to look at the reporting metrics… A 0.2% open rate? WHY??

There are several reasons why this might have happened but the first place to look is your reputation with the ISPs. IP warming plays a huge role in your reputation with the ISPs and email deliverability.

Wait, what is IP warming?

There are two basic pieces of the puzzle:

  • Deliverability

First, you need to earn the trust of the ISPs to receive all of the emails you are sending, and not block or hold your messages. It is essential to steadily increase the number of recipients you are sending to on a daily basis. You want to start with a small number of recipients and increase the number of recipients until you reach the maximum number of recipients in your database (except with AOL).

  • Inbox placement

This is the more challenging piece of the IP warming puzzle. Just because the ISPs are now accepting all or the valid emails you are sending doesn’t mean that your intended audience is actually seeing the information. While the ISPs are getting acquainted with your sending volume, they are also deciding where their customers should see your email. Should it be in the inbox or a junk/spam folder? 

When should IP Warming happen?

There are two different scenarios in which IP Warming is needed or can be helpful.

  • Brand new IP

You have obtained a new dedicated IP address. Generally when this happens, ISPs have no email sending history from this IP address.

  • Deliverability woes

You have had some deliverability issues and your reputation at the ISPs has been negatively impacted.

What metrics are being evaluated?

Some of the metrics that the ISPs are evaluating against when deciding if they should let your email through and where they should place it are:

  • Hard bounce rate – You want to have less than a 0.5% bounce rate while you are warming your IP. This lets the ISP know that you have a clean, well-maintained list.
  • Abuse complaints – In a perfect world, you wouldn’t receive any abuse complaints because you are only sending to recipients who have declared that they would like to receive your emails. However, people can be fickle and sometimes it’s easier to hit SPAM than it is to find the opt-out link. ISPs are looking for less than a 0.1% abuse rate.
  • Open Rate – ISPs are looking for your customers to engage with your emails. Are your recipients are actively opening the messages you send? Having an open rate that is consistent and growing will dramatically improve your reputation and can reduce the amount of time it takes to warm your IP.
  • Unsubscribe rate – Having recipients unsubscribe from an email is not necessarily a bad sign for IP warming. The ISPs still see this as an interaction with the email. It’s not as good as an open or a click, but much better than a spam/abuse complaint.

IP warming best practices

Okay, great, you’re thinking. What can I do to avoid a deliverability disaster? Start with these three simple practices and you should be in great shape.

  • Send to the right people. Since ISPs are looking for low bounce and abuse rates along with a high lever of recipient action. Every list of recipients is different. Every IP warming process will be a unique plan, but there are some Universal best practices. The best practice is to start IP warming with your recipients who have most recently opened and clicked and slowly incorporate less active recipients as you increase the send volume of your email sends.
  • Send the right content. Be sure to send engaging messages with a clear call to action during the warming process to encourage user’s to click in the message so that the ISPs are seeing interactions with the emails
  • Monitor your sends daily. IP warming can be full of ups and downs, so it is super important to know how you mailings are doing on a daily basis so that the warming plan can be modified before there are multiple bad days.


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