The Why, How & When to Email IP Warming

    by Kevin George
    IP warming

    Imagine that you are having your lunch, and you offer someone else to join your table for a week. Reflect on the consequences of the following two scenarios that can play from this moment:

    1. The person engages in a conversation with you. They are bombarding you with information that may interest you, but the volume is overwhelming you. They are also taking the liberty to taste the food from your plates. They are overstaying their welcome. This happens continuously for a week.
    2. The person begins with small talk or an icebreaker. They respect your boundary and are limiting the conversation to your capacity. Over the week, they are gradually increasing the amount of interaction you have with them. By the end of the week, you are comfortable talking with them & you don’t mind them having food from your plate (In fact, both of you are sharing food).
    In which of the above scenarios will you be, you are more receptive to the person on your lunch table? Scenario 2, right?

    A somewhat similar situation plays out with the ISP (Internet Service Provider) filters when you are using a new IP address to send your marketing email campaigns.

    The Concept behind IP Warming

    When an ISP filter observes a sudden spike in the number of emails sent from a specific IP address, it raises red flags and begins monitoring the activities. It compares the open rates with the unsubscribes and SPAM complaints & waits for someone to blacklist the sender, to take action regarding reducing the sender’s reputation for that IP address. This can severely affect your email deliverability, which in turn can hurt your business.

    On the other hand, send a small trickle of the marketing emails through the new IP address on the first day, and gradually increase the send volume over a few weeks. This way, the ISP filters get accustomed to your regular sending volume, and your sender reputation is maintained. The process is commonly termed as IP warming & most email marketers have no knowledge about it or mostly overlook it.

    Why do you need to conduct IP warming?

    Emails are the digital manifestations of the age-old practice of sending letters. Just like every letter is posted from a specific ZIP code and should carry the sender’s address, an email needs to be sent from an ISP. The ISP sends your email from your unique IP address, and the ISP at the receiver’s end delivers it to the addressed inbox.


    When you send an email to multiple addresses, you cannot do so from webmail providers such as Gmail, Yahoo!, or Hotmail. An ESP (Email Service Provider) has a range of IP addresses registered for sending emails in bulk. When you send an email from an ESP, you utilize an IP address from their range to send the email to your subscribers.

    ISP structure

    So when you are migrating from your current ESP to a new one, you will be utilizing a new IP range to send your emails. If you continue to send the same volume of emails as you did with your past ESP, you can observe a sharp dip in your email deliverability.

    Bad IP warming tactics

    (Source: Smart IP Warming)

    How to execute IP Warming?

    The process of IP warming is divided into two stages:

    1. Authenticating your emails
    2. Managing Email Send Volume.

    Authenticating your Emails

    Email authentication helps the ISP know that a specific email is sent from a credible source when it performs a reverse DNS lookup. You need to complete the following steps in order to authenticate your emails.

    1. The new IP address should be validated with the correct DomainKeys Identified Mail (DKIM)
    2. Update the IP address in your Sender Policy Framework (SPF)
    3. Ensure easy DNS lookup by mapping the hostname to your new IP address using CNAME and A Record

    Managing Email Send Volume

    As we stated earlier, for the ISP to build trust in the new IP address, you should begin with sending a small trickle of emails and gradually work on increasing the volume over a few weeks till you reach your expected sending volume. The goal is to send emails that will provide the maximum engagement, and convince the emails sent from the new IP address are solicited. The general breakdown of the email send volume ramping is:

    1. Put the best foot forward: Send those emails that your subscribers are expecting, such as welcome emails, transactional & behavioral emails, reminder emails, newsletters, and other relevant campaigns. Also, segment the list to send these emails to those who are constantly engaging with your emails.
    2. Start with Minimum: On the first day start with a small number of email volumes. Gradually increase the number on subsequent days. An acceptable schedule can be like this: Weekly Schedule of warming an IP
    3. Measure everything: How are your open rates? Are the emails facing soft bounces? Aim for 20% open rates, at least when warming an IP. Carefully measure the metrics of the email sends and modify your next day emails accordingly.
    4. Maintain Consistency: Sending a consistent volume of emails that perform well will help you establish a positive sending reputation quicker.

    Once you have reached your expected sending volume, you can cease the process.

    When to conduct IP warming?

    IP warming is only needed to be done when the IP address for your email changes, which may not be frequent. Two of the most common use cases are:

    1. Shifting to a static IP address: ESPs uses a wide range of IP addresses to send emails on behalf of their clients. If you choose to use a static IP, you are adding credibility to your emails, but you still need to warm the IP before you can use it.
    2. ESP migration: As you change ESPs, the IP range changes and the total number of emails sent by an ESP also changes. It is a good practice to warm the IPs yourself instead of relying on the ESP to do so.

    Wrapping Up

    Emails are the lifeline for most online brands and businesses. As long as the emails are safely reaching the intended inboxes, your subscribers are informed about the updates from your brand. A positive email sender reputation can only help you achieve that.

    If you ever face an IP warming issue and notice a decline in the reachability of your emails, follow the steps mentioned above with Atomic Mail Sender!

    Download the program and send mass emails 7 days for free!

    Written by:
    Kevin George
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