How to warm-up an email IP address

9 minute read

Why do I need to warm-up an IP address?

When you transition from one Email Service Provider (ESP) to another you will change IP addresses too – and possibly use an IP address that has never been used to send email before. Because the IP address is new, you will need to warm-up the new IP address and domain to ensure proper email delivery.

You effectively are going through the process of ensuring email providers see your sending IP address as reputable and trustworthy. IP address warmup creates a positive reputation for your IP address.

What about low volume senders?

Low volume senders are brands sending less than 50,000 emails per-month or sending primarily transactional emails vs. bulk marketing emails. And, as a low volume sender you can usually get by without following a warm-up schedule. But we do still recommend following the other recommendations in this article.

What do email providers consider as part of IP reputation?

There are many factors that determine your IP address sending reputation. Some of which include:

  • Valid email authentication – is the sender properly configured for DKIM and SPF?
  • Valid MX records – are the MX records valid?
  • Blacklists – is the sender’s IP address or domain on an email blacklist?
  • SPAM reports – was is the frequency of SPAM reports for emails from the IP address?
  • Bounce rate – is the sender attempting to deliver to a high number of invalid inboxes that bounce?
  • Engagement rate – is the recipient open the email or moving it straight to the trash?
  • Unsubscribe requests – how many unsubscribe requests are recipients making?

There are other factors that some email providers use for measurement too.

What happens when you don’t properly warm-up an IP address

When email systems, such as Microsoft, Gmail, AOL and others see activity from a new IP address they often delay delivery (known as a soft bounce) of those emails until the IP address appears to be trusted. Or worse, they will route the emails to the junk / spam folder.

  • High number of soft-bounces – it is likely that during the warm-up of your IP address you will see a high number of soft-bounces. A soft-bounce if a mailbox provider delaying the delivery of your message because it detects an unusual spike in volume from an an unknown IP address.
  • Decrease in inbox placement – as your IP reputation grows, so will your inbox placement (vs ending up in SPAM folder). Unfortunately this takes time and there is no set guidance. However, you can encourage your customers to white label your domain.

Email providers distrust new IP addresses because spammers often switch IP addresses and send high volumes of email.

This process, known as warming up an IP address, describes the steps you should take and what you should expect when sending email from a new IP address. This allows your sending reputation to build over time as your customers accept your messages.

Warming up an IP address can take 30-90 days.

Setting expectations – you will need to be patient

We’d love to tell you that warming up a new IP address is simple. Unfortunately it’s more art than science as each mailbox provider has their own rationale for how they trust a new IP address.

What about domain reputation?

When you move ESPs, you are likely transferring a domain that you are already sending messages on. Unfortunately, in our experience, the reputation of the IP address is at least equal that of the reputation of the domain. Or, put another way: even if your domain has a solid reputation from an existing ESP, you will still need to go through the process of warming up the new IP address(es) associated with that sending domain.

Before you start the IP address warm-up

Before you start your IP address warm-up, we recommend following the steps in this checklist.

Validate your email list

Before sending any email to warm-up an IP address we recommend verifying all of the email addresses on your sending list.

DailyStory has several built-in services, such as NeverBounce and Mailfloss. These services are used to validate a list of email addresses to ensure the addresses are still valid.

Follow best practices for inbox placement

Follow these best practices for email inbox placement and avoiding the junk folder.

At minimum, ensure your DKIM, SPF and MX records are configured correctly. At DailyStory we require this for all senders of any size.

We’re not playing buzzword bingo – SPF, DKIM and DMARC are all requirements for ensuring mailbox providers can trust you as a sender.

Have good sender hygiene

In addition to the technical setup of your email sending is correct, it’s also a good practice to ensure your emails follow the laws around email marketing. This includes making it easy for your recipients to optout.

Consider a dedicated IP address

Most ESPs, including DailyStory, will often use shared IP addresses. This simply means that you may be sharing the same sending IP address as someone else.

For many senders, this is not a problem. However, if you are sending to more than 100,000 unique email addresses you may want to consider a dedicated IP address.

How many IP addresses to I need?

The number of IP addresses you should associate with your sending domain is directly correlated to the daily volume you send:

Number of IPsDaily Volume
1-225,000 – 5,000,000
2-45,000,000 – 10,000,000
4-610,000,000 – 20,000,000
6-820,000,000 – 50,000,000

Avoid common blocklist words

We’ve put together a list of common block words that can cause problems for your emails. Get the full list as a Google Sheet or fork it from GitHub.

Use audience segmentation

Segmentation is the process of grouping your contacts by common characteristics. When it comes to warming up your IP address or sending domain you can use segmentation to create smaller audiences that you can use in the warm-up sequence:

  • Segment by email provider – Gmail, Hotmail, and Yahoo are common providers.
  • Segment by engagement – If you are bringing an existing list, who are your most engaged vs. least engaged email addresses.
  • Segment by region – Especially if you are international. This way you can send email at different times to different segments.

Test with your seed list

Before sending your emails to your customers, it’s a good idea to test with your seed list first.

Recommend Best Practices for IP address warm-up

Below are some recommended best practices for warming up a new IP address.

  • A slow warm-up is best – it is best to proceed slowly with a new email warm up. If you suddenly see a spike in soft-bounces or failed messages, it’s probably best to slow down the number of messages you are sending.
  • Your results may vary – different mailbox providers handle the warm up process differently. Some providers, such as Outlook, can take longer than providers such as Gmail.
  • Randomize the warm-up – if possibly try and randomize the warm-up across mailbox domains. For example, don’t group all AOL emails to send on the same day. Rather, break them up proportionally in your warm-up schedule.
  • Start with your most engaged recipients – these recipients are ones that routinely interact with your messages, click on your offers, etc. These recipients will help signal to the mailbox provider that your email is legitimate.
  • Distribute sends through-out the day – rather than sending all of your messages at once, try and distribute the sends through out the day. This will help ensure that mailbox providers don’t see a sudden influx, but gradually warm-up to your new emails.

Encourage readers to mark messages as “not spam”

Some mailbox providers will purposefully move email to SPAM to see if readers mark the messages as “not spam”. When warming up an IP address try and reach out to some of your best customer first and ask them to look for your emails.

Your reputation doesn’t transfer – unfortunately your sending reputation does not transfer with your domain, it is attached to the IP address. Mailbox provides like Gmail build reputation on domain plus IP address.

An example warm-up schedule

Putting together a plan for how you warm-up an IP address or set of IP addresses is important. And, you want to make sure you have the time to dedicate to monitoring your email delivery.

For a known email list, such as when transitioning to DailyStory from another Email Service Providers, we recommend starting small. If you start seeing delivery issues, back of your send rates.

What is an email delivery issue?

A delivery issue is when an email provider prevents delivery of your email. This can be a hard bounce (permanent failure) or soft bounce (temporary delay). In either case, these are indications that you should slow down your send rate.

For example, if you routinely send to 100,000 unique email addresses per month, we would recommend a sending schedule as follows:

Days 1 – 10 – initial warm-up

Send 1 percent day 1 and increment by 1%/day for the next 9 days. If any delivery issues occur step back 2% and build up again.

For a list of 100,000 unique email addresses this means sending to 1,000 on day 1, 2,000 on day 2, etc. By day 10, if everything is running smoothly, you should have sent to over 50% of your list.

Ideally you are sending to your highest engaged customers in days 1-10.

Days 11-30 – finish the initial warm-up

Increment the send rate by 2%/day for the next 20 days. Back off by 2-4% if any delivery issues occur.

During this phase you may also be sending additional emails to addresses that were sent during the initial warm-up.

Days 30 – 60 – increase the volume

At this point everyone on your list has received at least one email, but possibly more. You can now slowly start working up the volume of addresses per-send.

We recommend incrementing by 5%/send. Back off by 5% if any delivery issues occur.

Obviously your results may vary. But the above schedule is a good strategy to start with.

During IP Address Warm up

During the warm up process monitor your ESP’s delivery reports. You are likely going to see a high number of delayed / soft-bounce delivery. This is normal. Also monitor your reputation and that your IP address and/or domain have not been blacklisted.

If, during your warm up, you start seeing a high number of failures or bonces. It is best to step back to the last point in the warm up where you experienced a high delivery rate.

Common mistakes

Below are some common mistakes to avoid when warming up an IP address.

Send to non-engaged contacts

The most common mistake – and sometimes done on purpose – is attempting to reactivate unsubscribed or unengaged contacts. It’s important that when you bring data from one ESP to another that you bring this data with you, but that it is imported as opted out.

Too aggressive send rates to email providers

The next most common mistake is sending too many emails too fast. Some email providers, like Yahoo have limits on how many messages recipients can receive per day. If you start sending thousands of messages a day without properly warming up your IP address and sending reputation, you’ll end up in the junk folder.

What about email warm-up products?

In the last several years several vendors have started offering email warm-up services. In our experience these services are very hit-and-miss and we typically don’t recommend them. Unfortunately warming up an IP address takes time, but it’s time well spent for better results.

What about shared IP addresses?

If your ESP is using shared IP addresses for sending emails you should still consider warming up your sending domain.

What size list requires a warm-up?

We generally recommend warming up your email list if you have more than 50,000 unique email addresses. Lists lower than that require less process (while still following all the other recommendations). And lists larger than that get exponentially more complex. For example, it’s more difficult warming up a list with 1,000,000 address than one with 100,000.

Want to receive more great content like this for free?

Subscribe to our newsletter to get best practices, recommendations, and tips for digital marketers