Why Email Warm-Up Services are Shutting Down: An Insider’s Perspective

Email is still the main way people communicate online. Every day, 333 billion emails are sent and received, and that number is projected to reach 380 billion by 2025.

In this huge amount of information, email marketers have relied on "warm-up" services to build reputations and get emails delivered. Using these tools, marketers could send emails slowly to inboxes without setting off spam filters on new or "cold" email accounts. 

But new policy changes, especially from Google, are making things very hard.

As email companies crack down on their use, warm-up services that were once a vital part of many marketers' plans are being shut down. Security risks, API abuse, and anti-spam rules were factors in this change.

So, what’s behind this change? And what does it mean for email marketing's future?

Let’s take an insider’s look at why these services are shutting down and what it means for marketers everywhere.  

Let’s take an insider’s look at why these services are shutting down and what it means for marketers everywhere.  

However, this practice has come under scrutiny for its potential to manipulate sender reputation artificially, prompting ESPs like Google to take action.

Google has tightened its policies to combat misuse of its API. Many warm-up services used Google’s API to artificially inflate reputations by sending emails to inactive or fabricated accounts. This undermined Gmail’s commitment to authentic communication and violated its terms of service.

Spam remains a colossal problem, accounting for 85% of global email traffic in 2023. Warm-up services often skirted anti-spam measures by sending irrelevant or unsolicited emails, which conflicted with Google’s mission to deliver relevant content.

Warm-up tools frequently required access to users’ email accounts, posing significant risks:

• Unauthorized Access: Third-party tools often demand account credentials, which can lead to breaches.
• Phishing and Malware: Gmail blocks over 15 billion malicious emails daily, and compromised accounts amplify this threat.

Warm-up services manipulated sender scores by interacting with fake or inactive accounts, eroding trust within email ecosystems. Google aims to ensure reputation is earned through genuine engagement rather than artificial tactics.

Google prioritizes a spam-free, relevant inbox experience. By eliminating warm-up services, the platform ensures users receive emails that are valuable, not spammy or artificially elevated.

This crackdown pushes marketers toward legitimate strategies like segmentation, double opt-ins, and creating engaging, permission-based content. These practices build lasting relationships and improve long-term deliverability.

With warm-up services off the table, marketers need to pivot to sustainable methods for maintaining email deliverability. Here’s how:

Start small by sending emails to a limited, engaged audience. Gradually increase your volume while monitoring open and click rates to establish trust organically.

Some services now use IMAP protocols instead of APIs. While these can bypass Google’s restrictions, marketers should remain cautious as similar policies could extend to these methods.

• Segmentation: Send targeted content to specific groups for higher engagement.
• Double Opt-Ins: Confirm subscribers’ intent to receive emails, ensuring quality over quantity.
• Content Quality: Craft valuable, personalized emails that resonate with recipients.

For now, platforms like Outlook, Zoho Mail, and Yahoo! Mail allow automated warm-up tools. While these are viable alternatives, marketers should anticipate similar restrictions from these providers.

1. Prioritize Engagement Metrics: Focus on open rates, click-through rates, and subscriber interactions. High engagement signals ISPs that your emails are valuable.
2. Maintain a Clean Email List: Regularly remove inactive subscribers and invalid addresses to reduce bounce rates and maintain a healthy sender reputation.
3. Invest in Authentication Protocols: Implement DMARC, DKIM, and SPF records to authenticate your domain and increase deliverability.
4. Avoid Spam Triggers: Stay clear of spammy phrases like “Free money” or “Guaranteed income” in subject lines and content.
5. Leverage Double Opt-Ins: Require subscribers to confirm their subscription, ensuring they genuinely want your emails.
6. Monitor Your Sender Reputation: Use tools like Google Postmaster, SenderScore, or Barracuda to track your domain’s health and identify any issues early.
7. Use Quality Content and Personalization: Tailor emails to the recipient’s preferences and behavior. Personalized emails can significantly boost engagement.
8. Test Before You Send: Use email testing tools to check for spam triggers, broken links, or design issues before launching a campaign.

Google’s decision to ban warm-up services marks a shift toward more ethical and user-focused email marketing practices. While this may challenge traditional cold-email strategies, it encourages marketers to focus on meaningful engagement and genuine connections.

By adopting compliant, transparent methods, marketers can achieve better results without compromising trust or security. This evolution not only safeguards users but also strengthens the long-term effectiveness of email as a marketing channel.

Google banned these services to combat spam, prevent API misuse, and improve user security. These tools often sent irrelevant or fake emails, violating Google’s policies.

Marketers can no longer rely on automated warm-up tools to build sender reputation. Instead, they must adopt ethical practices like gradual email scaling, segmentation, and double opt-ins.

Yes. Manual warm-up methods and IMAP-based tools are alternatives. However, marketers should be cautious, as similar restrictions could apply to these solutions in the future.

Sender reputation is a score assigned by ESPs based on email engagement, bounce rates, and complaints. A strong reputation ensures higher deliverability and keeps emails out of spam folders.

Currently, other providers like Outlook and Zoho allow warm-up services, but this may change as these platforms adopt stricter anti-spam measures.

Focus on best practices like creating high-quality, relevant content, segmenting your audience, and using authenticated domains to build trust naturally.

Spam filters use algorithms to identify suspicious patterns like high volume, unengaged recipients, or spammy language. To avoid them, maintain good practices and monitor your metrics.

Typically, manual warm-up takes 3–6 weeks. Begin with a small volume and gradually increase while ensuring high engagement rates.

Engagement metrics like opens and clicks show ESPs that recipients value your emails, improving deliverability and boosting sender reputation.

Use tools like Google Postmaster, HubSpot, or Mailchimp analytics to track engagement, bounce rates, spam complaints, and reputation scores.