What are the best practices for warming up new email domains with Yahoo and Microsoft?
Michael Ko
Co-founder & CEO, Suped
Published 28 Apr 2025
Updated 16 Aug 2025
6 min read
Warming up new email domains with major mailbox providers like Yahoo and Microsoft is a critical step in establishing a strong sender reputation and ensuring high deliverability. Without a proper warmup, your emails risk being flagged as spam, blocked, or sent straight to junk folders, negating your outreach efforts. It's about gradually building trust with email systems, showing them that you are a legitimate sender sending wanted mail.
The process isn't just about sending volume, but also about cultivating positive engagement and adhering to strict authentication standards. While general guidelines exist, Yahoo and Microsoft have specific nuances you should understand. My goal here is to outline a comprehensive approach to help your new domains achieve optimal inbox placement.
Setting up authentication and infrastructure
Before you even consider sending your first email from a new domain, robust email authentication is non-negotiable. This foundation proves your legitimacy to mailbox providers. You need to properly configure SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance).
SPF and DKIM verify that your emails are coming from an authorized source and haven't been tampered with. DMARC builds on these, allowing you to tell mailbox providers what to do with emails that fail authentication, as well as providing valuable reports on your sending. For a deeper dive into these protocols, explore a simple guide to DMARC, SPF, and DKIM.
Microsoft, particularly, has stringent requirements for high-volume senders, including mandatory DMARC policies. Setting up a DMARC record, even with a policy of p=none, is an important first step to gather data and ensure proper alignment before enforcing stricter policies like quarantine or reject.
Essential DMARC setup
Implementing a DMARC policy from day one is crucial for new domains, particularly with providers like Microsoft and Yahoo. Start with a p=none policy to monitor email authentication without affecting delivery, then gradually move to p=quarantine or p=reject as your confidence grows. This demonstrates commitment to email security.
The core of domain warmup is a gradual increase in sending volume. Instead of sending a large number of emails from day one, start small and slowly ramp up your volume over several weeks. This methodical approach allows mailbox providers to assess your sending patterns and build a positive reputation. Start by sending to your most engaged subscribers, who are highly likely to open and click your emails. This positive engagement signals to Yahoo and Microsoft that your emails are wanted and valuable, helping to avoid the spam folder.
It's also important to understand that your IP and domain warm-up strategy should align with your email sending habits. If you plan to send daily, then a daily gradual increase is appropriate. If you send weekly, then a weekly increase. Consistency is key. You can also target specific mailbox providers during the warmup by ensuring a balanced send across different providers.
Engagement focused: Yahoo places a significant emphasis on recipient engagement. Prioritize sending to users who actively open, click, and reply to your emails. This positive interaction directly influences your sender reputation.
Feedback loops: Sign up for Yahoo's Complaint Feedback Loop to quickly identify and remove users who mark your emails as spam. High complaint rates can lead to blocklists (or blacklists).
Microsoft's perspective
Sender score and SmartScreen: Microsoft (Outlook, Hotmail, Live) heavily relies on internal scoring and their SmartScreen filter. Beyond authentication, ensure your content is clean and doesn't trigger spam filters. Avoid suspicious links or excessive images.
SNDS and JMRP: Register for the Smart Network Data Services (SNDS) and Junk Mail Reporting Program (JMRP). These tools provide insights into your sending reputation and spam complaints directly from Microsoft, which are invaluable for troubleshooting.
Monitoring and adapting your strategy
Monitoring your domain's performance during the warmup phase is just as important as the sending itself. Pay close attention to key metrics such as open rates, click-through rates, bounce rates, and crucially, spam complaint rates. A low spam complaint rate is vital; both Yahoo and Microsoft expect it to be well below 0.1% for optimal deliverability. If you see spikes in bounces or complaints, it's a sign to slow down your sending volume and investigate the cause.
Regularly check common email blocklists (or blacklists) to ensure your new domain or IP hasn't been listed. Being on a blocklist can severely hinder your deliverability. If you find your domain (or IP) has been blocklisted, immediately cease sending, identify the root cause, and follow the delisting procedures. You can also refer to our guide on what happens when your domain is on an email blacklist.
Using DMARC reports is another critical aspect of monitoring. These reports provide invaluable feedback on your authentication results and potential abuse. Understanding and troubleshooting DMARC reports from Google and Yahoo will help you refine your sending practices and maintain a healthy domain reputation. Consistent positive performance is what truly builds trust with these major providers.
Metric
Why it matters
Yahoo & Microsoft expectations
Open rate
Indicates recipient interest and content relevance.
High open rates are crucial. Aim for above 10-15% during warmup.
Spam complaint rate
Directly impacts sender reputation. High complaints lead to blocking.
Keep below 0.1% to avoid blocklisting (or blacklisting). Ideally, near 0% for new domains.
Bounce rate
Indicates list hygiene and validity of email addresses.
Maintain very low bounce rates. Remove invalid addresses immediately.
Content and list hygiene
Beyond the technical configurations, the actual content and nature of your emails play a huge role. For new domains, it's advised to send simple, text-based emails initially. Avoid heavy HTML, excessive images, or numerous links that can trigger spam filters during the critical warmup period. As your reputation grows, you can gradually introduce more complex designs.
List hygiene is paramount. Ensure your recipient list consists of truly opted-in individuals. Sending to old, unengaged, or purchased lists is a fast track to being blocklisted (or blacklisted) and will undermine your warmup efforts. Implement double opt-in if possible, and regularly clean your lists to remove inactive subscribers or improve email deliverability with Microsoft and Yahoo.
Finally, be patient. Domain warming is not a quick process; it typically takes several weeks to months to build a solid reputation, depending on your sending volume and the consistency of your positive engagement. Rushing the process can set back your progress significantly. Think of it as a long-term investment in your email program's success.
Views from the trenches
Best practices
Start with extremely low volumes, sending only to your most engaged subscribers who are likely to open and click.
Implement SPF, DKIM, and DMARC from day one, starting DMARC with a p=none policy to monitor authentication.
Gradually increase your sending volume and list diversity over several weeks, watching engagement metrics closely.
Common pitfalls
Sending high volumes too quickly from a new domain, which immediately triggers spam filters.
Sending to unengaged or purchased lists, leading to high bounce rates and spam complaints.
Expert tips
Expert from Email Geeks says: "Dedicated IPs cannot be effectively warmed without their associated domains. Warming plans are highly customized, relying on historical traffic, sender reputation, and email volumes, meaning there is no universal warming strategy."
Marketer from Email Geeks says: "We are trying to establish two new domains to replace ones affected by DKIM replay attacks, with current mail routing through a single unaffected domain."
Expert from Email Geeks says: "If the email content is genuinely anticipated by recipients, contact Yahoo! and Microsoft postmasters beforehand to outline your sending plan. Google's machine learning will handle its own assessment, so direct communication isn't typically needed there. Focus on ensuring recipients know to check spam folders and add your new From addresses to their address books, and manage mail queues as needed."
Expert view
Expert from Email Geeks says: Dedicated IPs cannot be effectively warmed without their associated domains. Warming plans are highly customized, relying on historical traffic, sender reputation, and email volumes, meaning there is no universal warming strategy.
May 20, 2022 - Email Geeks
Marketer view
Marketer from Email Geeks says: We are on a shared IP ESP.
May 20, 2022 - Email Geeks
Summary of best practices
Warming up a new email domain for Yahoo and Microsoft requires a strategic blend of technical setup, careful sending practices, and continuous monitoring. There's no single magic formula, but by prioritizing strong authentication, gradual volume increases to engaged recipients, and diligent reputation management, you can successfully establish your domain as a trustworthy sender.
Remember, building a good sender reputation (and avoiding issues like being added to a blacklist or blocklist) is an ongoing effort. Consistency and responsiveness to feedback loops are key to maintaining long-term email deliverability with these major providers. By following these best practices, you set your email program up for success from day one.
Microsoft and 
Yahoo. Start with a p=none policy to monitor email authentication without affecting delivery, then gradually move to p=quarantine or p=reject as your confidence grows. This demonstrates commitment to email security.
