What is IP address warmup? MAX Video

What is an IP warmup?

Your GetResponse MAX account comes equipped with one or more sending IP addresses that have never been used before. This means that they have no sending history.

IP warmup is a process during which the IP earns its reputation with Internet Service Providers (ISPs). The ISPs need to see that you send relevant and permission-based emails before they will begin to trust your bulk mailings to be sent through to inbox folders.

The same applies to the sending domain if one has never been used before, or has not been “paired” with the specific IP address before.

When and why do I need an IP warmup?

ISPs (inbox service providers, like Google, Yahoo, Microsoft) are always looking at messages from new IPs with some level of suspicion. They want any sender (no matter what business type or mailing content) to first demonstrate that they are legitimate and compliant with anti-spam rules.

An IP address warmup is required, when you:

  • start working with a new ESP (email service provider, like GetResponse) on a dedicated IP,
  • re-start sending after a break,
  • start sending from a new IP address,
  • start using a new sending or from domain (even if it is added to an IP address already in use, warmup is still recommended).

Note: New sending domain warmup is not a definitive “must”, but can be very useful for your deliverability, especially for Gmail and Yahoo inboxes. It is usually performed quicker than IP warmup. The guidelines for it are similar: engaged recipients, consistent volume and frequency, but you can start from a higher volume and increase it a bit quicker.

If you are in the process of migrating from a different ESP and are not planning to change your from field domain, we recommend you to have a “transition period” of 1-2 weeks, when you already start warmup at GetResponse, but also still send some messages from your previous ESP. That will help with the from field warmup.

To warm up a new from field start by splitting the recipients of your message and send about 90% of them a message with the old from field, 10% of them a message with the new from field. With every new message, gradually increase the ratio toward the new from field.

Why does it have to be slow?

Spammers are very often using the same pattern: they purchase a new domain and IP and try to bulk-send as much mail as possible before getting blocked.

ISPs have algorithms and different antispam and security mechanisms to prevent that. One of them is putting everyone on neutral or even low sender reputation in the beginning. You have to prove that you are a good, trustworthy sender, and the way to do that is by slowly and consistently warming up your IP, showing the ISPs that you are ready to play by their rules.

Note: you (as a sender) do not have a financial relationship with ISPs, therefore they -sadly – do not have any obligations to deliver 100% of your mail. ISPs’ highest priority is always the security of their own clients: owners of the inboxes. That’s why they are more likely to be overprotective and make false-positive rejections, until you have proven to their algorithms that you are a sender with good intentions, a good list, and good email marketing practices.

During the account warmup, it’s important to start with low volumes and send to the most active contacts first to start building a solid reputation.

To do this, identify who on your list most recently opted-in and engaged, and always send to those contacts first during warmup.

Organic list growth is highly recommended as it generates responsive and verified subscribers, especially if the subscriptions are processed in the double opt-in mode.

We strongly advise you follow the warmup schedule. Avoiding it may lead to serious deliverability problems and can damage your reputation for a long time.

Key characteristics of a successful warmup:

  • Patience: warm up slowly with a gradual increase, according to your warm-up plan.
  • Engagement: send to the most active recipients first, most likely to engage with your emails by opening them, clicking the links, etc.
  • Consistency: stick to the warmup plan, don’t stop or suddenly change volume in the middle of it.

Many ISPs look at the ratio of how many recipients engage with received messages to the total amount of messages sent. If you send to your most engaged contacts, this ratio will be high. ISPs notice these good results + see that you are starting slowly + see that you are consistent = they are no longer suspecting you can be a spammer, meaning you can now send more without deliverability issues.

The plan below should work for most users, but we need to remember that there are many factors which can influence the warmup process. Your Customer Experience Manager and Deliverability Team will help you monitor the results and act accordingly as to any possible inconsistencies.

DayGmailYahoo (Yahoo, AOL, Verizon: altogether)Microsoft (Hotmail, Outlook, Live: altogether)Polish ISPs (Onet, Interia, WP: each one separately)French ISPs (Free, Laposte, Orange: each one separately)Other

As you can see, the warmup plan also depends on the ISP, so different parts of your list can be warming up faster than the others. It’s necessary to remember that each mailbox provider has its own set of rules of how fast they can trust a sender. It may seem like extra steps, but it pays off because eventually you will end up with much better results all across the internet community.

Note: Gmail relies strongly on their machine learning system. They are not as likely to block you from the very beginning as some other ISPs, but if they do, you are in trouble: it takes a long time to gain back the reputation and a manual delisting request is not an option with them. That’s why we suggest starting with a very low volume to Gmail addresses in the beginning. 

Alternative “simplified” schedule if you cannot split your list by ISPs:

DayVolume to all ISPs

The simplified schedule requires you to be even more careful, ready to update the schedule if any of the ISPs do not seem to like it. It is more difficult to troubleshoot, so if possible, we advise you to use the split by ISPs schedule instead.

Note: don’t forget that frequency is key here, you have to stick to the schedule and send a message every day. It is important not to have sudden pauses, that can confuse ISPs’ antispam algorithms and negatively influence your sender reputation.

How to prepare the list?

The best way to prepare your list before sending is to segment it. You have to segment it in a way ISPs will like, in such a way that algorithms of each particular ISP pick up a lot of (as much as possible) engagement from the recipients of your messages. Ideally, you should use 2 criteria for segmenting: engagement and ISPs.


The level of engagement is based on subscribers interactions with your content (i.e. messages). Depending on how you used to manage your list and what historical metrics you have available, it might mean different things, however, the main idea is to extract the most engaged contacts possible. Those could be:

  • Contacts who clicked the links within the last 1 month, 2 months, 3 months, etc.
  • Contacts who opened the messages within the last 1 month, 2 months, 3 months, etc.

Note: Clicks have recently become a much more reliable metric, especially due to Apple’s introduction of their new privacy policy. We highly recommend paying more attention to clicks than opens.

Example: if you have click data available, you can start your warmup by mailing the group of contacts who have clicked on the links within the last 1 month, then add clickers from 2 more months, then include contacts who have opened the messages within the last 3 months, then within half a year, etc.

If click data is unavailable, or the number of such contacts is way too small, you can start with the data you have, for example, openers from last month, then add openers from 2 months, 3 months, 6 months, etc.

Warmup is becoming especially dangerous if the engagement data you have is older than 1 year. In this case, you must verify your list with a third-party tool and start the warmup from the most recent subscribers.


After you have created “most engaged” segments of your list, it is highly recommended to also segment your list by ISPs (domains) such as Google (Gmail), Yahoo/AOL, Microsoft (Hotmail, Outlook, Live), business email addresses and other domains.

It is possible to warm up an IP without it, but segmenting a list in this way will help you keep track of the volume sent to particular ISPs and react quickly in case of blocks or deliverability issues with one of them.

What do I send?

For a successful warmup it is crucial to create proper messages. The main goal here is to generate as many interactions as possible: opens, click, and replies (they are also beneficial for your IP warmup). Therefore, the messages should be wanted, have quality content, and a strong (but not imposing!) call for action.

At the same time, the message should be “safe” in the eyes of anti-spam filters, meaning it should not be overflown with links and “spammy” words. It should also have a healthy text-to-image ratio.

A good idea is to check your previous email communications with clients, find the most successful campaigns and base your warmup emails on them.

If you are certain that your opt-in pages are properly secured and the traffic you are driving to them is top-notch quality (meaning new contacts who end up on your list are very engaged), you can also send out welcome messages to them during warmup, but keep an eye on the numbers.

During warmup: monitoring and taking action

Once the warmup schedule is prepared and first messages are sent out, what do you do now? You need to monitor your results closely, day-by-day and after each send.

Blocks are to be expected

You can almost certainly expect blocks on some domains and/or some spam placement in the beginning. That is due to the complicated nature of the warmup process: it takes time for a sender and ISPs’ anti-spam filters to learn about each other and become “friends”.

There is almost never a warmup that has no kinds of blocks, but as long as you are monitoring your metrics and react timely, all those issues will resolve in a while.

What to do when blocks happen?

For spam placement, the best way to show the ISPs’ filters that they have mistakenly placed this message in this folder, is to drag the messages out of spam and into your inbox, adding the sender to contacts or a safe sender whitelist.

This is exactly why you should start from the most engaged segments: if the message is wanted, the chance the subscribers will actually search for it within their inboxes and move back to the main folder is much higher.

If the spam issue is reaching a larger scale, double-check the content of the messages, make sure the links are secured and their amount is not overwhelming, check message content for “spammy” words, check text-to-images ratio. Also review the recipients group once again.

If you see that an ISP started blocking or delaying your messages, don’t panic: together with your Customer Experience Manager and with the help of Deliverability Team check the bounce logs you are receiving.

For most of them the correct course of action will be to continue sending but refrain from increasing the volume sent to this domain for a while. You will be able to reach your desired IP volume, but it will happen a bit later. You might need to lower the volume, but in such cases it is also important not to stop mailing completely. Consistency is key here, and a sudden lengthy break can confuse the ISP even more.

Some of the bounces can indicate more serious issues which Deliverability Team will have to mitigate directly with the mailbox providers or which will require you to review your list hygiene practices.

Other types of metrics to pay attention to

  1. Click rates – the higher the better. They can vary greatly depending on your type of business. Make sure they are similar to the levels you have reached before and monitor any rapid increases or decreases.
  2. Open rates – low open rates should be investigated, they can be a sign of spam placement.

Note: While open rates vary greatly depending on the business type, previously marketers would consider reaching about 20% unique open rate as a good result. Now, however, with the introduction of Apple’s MPP, opens are not as great of an indicator as before and have become very unreliable. We advise you to pay more attention to clicks, conversions, purchases, etc. Read more about Apple’s MPP and its influence on your mailing statistics here.

  1. Complaints – complaints to sends ratio (per domain) should be under 0.1%. Ideally, it should be very close to 0 at the beginning of warmup.
  2. Hard bounces – the lower, the better. If there are more than 2-3% of them, something is likely wrong with your data. Just as with complaints, at the beginning of warmup, you should aim at having close to 0 hard bounces.
  3. Spamtrap hits – spamtraps are email addresses used by ISPs and security providers to “trap” senders with bad lists acquisition or list hygiene practices. They should not be on your email list and always indicate some kind of bad list practice, which can lead to an unsuccessful warmup. Your Customer Experience Manager or our Deliverability specialists can check this for you.