Email Warm-Up: IP & Domain Warming Strategy

Are you just starting to send emails, transitioning to dedicated infrastructure, or switching your sending domain? Don’t overlook a key step – the warm-up process!

Warming up an IP address or sending domain before large-scale marketing email campaigns is a strategic approach to gradually building a positive sender reputation. This helps prevent deliverability issues like messages landing in spam folder, bounces, or being blocked by recipient servers. This process is critical when sending from new IP addresses, newly registered domains, or significantly increasing your email volume.

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Email Sending Warm-up and Email Deliverability

Before a receiving server accepts large volumes of emails from a new source, it evaluates the sender’s reputation, including both the IP address and domain. Messages without a solid reputation score may be rejected or classified as spam.

The warm-up process involves initially sending a small number of emails to well-engaged, highly identified recipients and then gradually increasing the volume over time. This process can take anywhere from a few days to several weeks, depending on the scale of the planned send and user engagement. It’s often tailored per provider to meet the specific requirements of global ISPs.

A proper warm-up allows you to build a positive sender reputation in a controlled manner. It eventually enables large-scale email campaigns with minimal risk of deliverability issues. When done correctly, it significantly increases the likelihood that messages will land directly in the inbox rather than the spam folder

What Is the IP Warm-up Process?

The anti-spam filters used by global providers like Gmail, Yahoo, and Microsoft evaluate the IP address from which emails are sent. When security algorithms recognize a sender’s IP as trustworthy, recipient servers are more likely to accept those messages.

However, new IP addresses that are used for mass email campaigns right away can quickly be blocked or flagged as spam by providers. This happens because the ISP may interpret the IP as a source of harmful content and reject it to protect its users. Additionally, new IPs are more likely to end up on global blacklists, which severely impacts deliverability.

When Should You Warm Up an IP Address?

Whenever you start sending mass emails from a new IP, it’s crucial to go through a proper warm-up process. This is especially important when:

• You’re working with a new Email Service Providers (ESP) and are assigned a dedicated IP address to your infrastructure;
• You’re resuming email sending after a long break;
• You typically don’t send messages to recipients at a specific provider but plan to increase the volume of your messages sent to users.

Each situation involves a significant increase in traffic to a provider from a dedicated IP, making warm-up essential to ensure smooth deliverability.

Contact us if you’re using a dedicated IP with EmailLabs, and we’ll prepare a personalized warm-up plan for you!

What is the Domain Warm-up Process?

Domain warm-up, similar to the IP process, involves gradually increasing the number of emails sent from a specific sender. This action is significant when changing your “From” domain. Such a modification is often viewed suspiciously by ISPs, which can flag the domain as a potential spam source. As a result, domain reputation – tracked in tools like Google Postmaster – can decrease, and the domain may even end up on global blacklists.

By gradually ramping up your domain’s sending volume, you allow recipient servers to recognize it, which is key to building a positive sender reputation. This significantly increases the chances of your emails landing in the inbox rather than the spam folder, improving both deliverability and the effectiveness of your campaigns. Additionally, it helps avoid the risk of messages being blocked or rejected by mail servers, which could harm your domain’s reputation in the long term.

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Maintaining Consistency in Email Headers

Your domain is not only visible in the “From” field but also in other email headers like DKIM, DMARC, and SPF. If you’re changing any of these records, remember that this might also require a warm-up process. Even if providers are familiar with your domain in one header, it may be unfamiliar in another, making it a new and unrecognized element. Therefore, it’s important to implement these changes gradually.

We strongly recommend ensuring domain alignment across all email headers, including “From,” DKIM, and Return-Path. Domain alignment means that the domains in these headers match or closely correspond to each other, creating a consistent identity. This practice strengthens your email’s trustworthiness, supports DMARC policies, and reduces the likelihood of your messages being flagged as suspicious by spam filters. When implementing changes to achieve alignment, it’s best to follow a gradual warm-up process.

Warming up involves ensuring that domains or subdomains are correctly configured and slowly added into the sending flow. A best practice is to gradually shift the traffic – start by changing the domain in the headers for, say, 5% of your emails, and then incrementally increase the percentage until you reach 100%. This approach allows you to integrate the new information smoothly without triggering security filters.

The Role of Warming Up in Building Sender Reputation

Your sender reputation is built on the quality of your email campaigns, which are evaluated by algorithms based on factors like proper configuration, security protocols, and recipient engagement.

By gradually warming up your sending volume after changes such as a new IP address or domain, you begin the process of establishing a positive reputation. Over time, as engagement metrics improve and complaint rates remain low, your reputation as a sender will strengthen, increasing the likelihood that your emails will successfully reach inboxes in the future.

How to Prepare Your Email List for Warm-up

Preparing your email list for a warm-up is critical, especially if you plan to send a high volume of emails. Segmenting your audience based on their engagement and the receiving domains is key to building a strong sender reputation and optimizing deliverability. Gradually increasing the emails sent is essential to avoid potential mailing issues.

Engagement-Based Segmentation

Start by analyzing your entire subscriber base in terms of engagement levels. Focus on the most active recipients – those who frequently interact with your emails. Begin the warm-up by sending messages to contacts who have shown the highest open and click-through rates. As the process progresses, expand the volume to include other groups based on their last interaction with your messages.

ISP Segmentation

Segmenting your list by Internet Service Provider (ISP), such as Google (Gmail), Yahoo, Microsoft (Hotmail, Outlook, Live, etc.), and corporate domains, allows for more precise monitoring and swift action if deliverability issues arise. This ISP-specific segmentation helps manage the sending process more effectively and builds a stronger sender reputation.

When preparing your email list, ensure it includes recipients using different mailboxes (a mix of domains). Avoid sending all your messages to users of a single provider, like Gmail. Following these practices can prevent large volumes from triggering spam filters at any ISP, ensuring a smoother warm-up process and better long-term deliverability.

Warm-up Process: Step by Step

Now that you understand the importance of warming up your sending and how to prepare your recipient list, the final step is planning your email campaign.

Below is a template you can use to guide your warm-up process. However, remember that this example should be tailored to your specific audience, so take the time to review and adjust it accordingly.

	Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7
Week 1	100	300	500	1 000	3 000	10 000	20 000
Week 2	40 000	60 000	80 000	100 000	150 000	200 000	300 000
Week 3	400 000	500 000	600 000	800 000	1 000 000	1 100 000	1 200 000
Week 4	1 500 000	3 000 000	4 000 000	5 000 000	6 000 000	7 000 000	8 000 000

During the warming process of your email domain or IP, it’s worth spending time on monitoring and analyzing performance metrics. This phase requires particular attention, as it directly impacts whether your sender’s reputation will be positive or negative.

Google Postmaster Tools is a free tool that enables senders to monitor and analyze various aspects of their email performance within Gmail. It provides insights into IP and domain reputation, delivery errors, spam rates, feedback loops, and authentication results, allowing senders to identify and address issues affecting their sender reputation.

Email Deliverability Report Analysis

The first and most important step is to check if the recipient servers continuously accept emails you send. Regularly monitor data using analytics tools such as Google Postmaster Tools or deliverability reports in the EmailLabs dashboard. 

Pay special attention to statuses such as “OK” (indicating successful acceptance by the recipient server) and “Deferred,” which may suggest potential reputation issues or restrictions imposed by recipient servers, necessitating immediate action.

Email Providers Blockades

During the warming phase, email providers may also block your IP or domain. Such blocks can result from violations of anti-spam policies or excessive sending rates. It’s crucial to quickly identify these situations and, if necessary, contact the provider for detailed information and to potentially unblock your IP or domain.

Email Sending Limits

Another action that email providers may take is to impose sending limits. This mechanism restricts the number of messages delivered within a specific timeframe. If limits (rate limits) are applied, you should immediately respond by reducing your sending rate and then gradually increasing it according to the recommended guidelines. Ignoring these limits can lead to more severe issues, such as complete sending blocks.

Email Service Provider	Daily Sending Limit	Hourly Sending Limit	Recipient Limit per Email	Attachment File Limit	Limit Exceeded Alert
Gmail	2 000	–	–	25 MB	You have reached a limit for sending emails.
Microsoft Outlook	5 000	–	500	20 MB	Email sending limit exceeded.
Microsoft Office 365	10 000	1,800/30 per minute	500	150 MB	Email sending limit exceeded.
Zoho Mail	250 – 2 000	–	–	20 MB to 1 GB	Mail rate exceeded.
Yahoo Mail	500	100	100	25 MB	A limit has been met.
GoDaddy	500	–	–	30 MB	“The server response was: User _____ has exceeded its 24-hour sending limit.” “Messages to 25 recipients out of 25 allowed have been sent.” “System.Net.Mail.SmtpException: Mailbox unavailable”
BlueHost	–	150	–	50 MB	Speed limit exceeded.
Dream Host	–	100	–	40 MB	You will receive an email notification.
Hostinger	–	200 via Webmail500 via SMTP	–	50 MB for inbound email35MB for outbound email	–
Host Gator	12 000	500	–	20 MB in Reseller Hosting SMTP30 MB in Windows Hosting SMTP	The email limit has been exceeded. Attempt to send the email at a later time.
Rackspace	10 000	–	–	50 MB	–

source: https://www.saleshandy.com/

Email Engagement Metrics

Remember that even during the warming process, it’s essential to monitor engagement metrics, such as open and click rates. Low performance in these areas may signal deliverability, qualification, or content issues, which could negatively impact your ongoing efforts. In such cases, it’s important to adjust your sending strategy or content to improve recipient engagement, as this can significantly enhance the effectiveness of your email marketing campaign.

Regular monitoring and quick responses to issues are fundamental to warm-up your domain or IP effectively. This approach will not only help you build a positive sender reputation but also minimize the risk of deliverability problems in the future.

Case Study: Optimizing Email Marketing Campaigns with IP Warm-Up

The client sought to transition to a new EmailLabs account to optimize email operations while maintaining the same sending domain. As part of this migration, new IP addresses were assigned, requiring a warm-up process to establish a strong reputation and avoid deliverability issues.

The client prioritized a smooth infrastructure migration without compromising email quality. With a maximum volume of 100,000 messages, their objective was to complete the IP warm-up process within a week.

The IP Warm-IP Process

Step 1: Comprehensive Analysis of Client’s Email Activity

To kick off the project, we gathered detailed insights into the client’s email practices:

• Sender domain reputation: Evaluated historical performance and credibility.
• Email volume: Assessed sending habits, including maximum batch size.
• Domain distribution: Analyzed the composition of the recipient list to ensure diverse domain coverage in warm-up batches.

Step 2: Crafting a Tailored Warm-Up Plan

Using our proprietary tools, we developed a warm-up schedule starting with 250 emails per day, gradually increasing the volume

	Day 1	Day 2	Day 3	Day 4	Day 5	Day 6	Day 7
Week 1	250	870	2530	6400	16060	40130	100100

Step 3: Real-Time Monitoring of Warm-Up Performance

Monitoring was the cornerstone of the process. Key actions included:

• Status analysis in EmailLabs: We tracked spam bounces and deferred statuses daily to ensure they remained within acceptable thresholds.
• Issue investigation: For anomalies, such as increased spam bounces, we conducted root-cause analyses to address potential problems promptly.

Step 4: Additional Monitoring Tools

• IP Reputation: Continuous evaluation using monitoring tools ensured the new IP maintained its high reputation.
• Blacklist Monitoring: We tracked global blacklists to verify the absence of the client’s IP, preventing deliverability disruptions.

Daily data reviews allowed us to fine-tune the warm-up strategy, adjusting email volume increases based on performance metrics.

Results of the IP Warm-Up

• Timely Completion: The warm-up process was completed within the scheduled timeframe without any significant issues in EmailLabs statuses.
• Good IP Reputation: The IP maintained a positive reputation and avoided blacklisting.
• Optimal Deliverability: High-volume sends (100,000 emails) faced no restrictions or additional scrutiny from providers.
• Reliable Infrastructure: The client now enjoys a robust email setup with excellent deliverability and accurate message classification.

Our team continued monitoring the client’s account for several days post-warm-up to ensure smooth operations during regular campaigns. Focus areas included deliverability rates, spam bounces, and IP reputation.

IP Warm-Up: Conclusion

Today, the client runs stable and successful email campaigns with high deliverability and positive message classification. The warm-up process was a success, enabling the client to achieve their email marketing objectives without compromising communication efficiency.

Effective Email Marketing With IP and Domain Warm-up

Sending emails without warm-up poses risks of blocks and restrictions, which can lead to low campaign effectiveness. In contrast, implementing the warming-up process allows you to build a positive sender reputation, enhances message deliverability, and minimizes the risk of delivery issues. In the long run, it is essential for any campaign aiming to achieve high effectiveness and recipient engagement.