How do I successfully navigate the Microsoft IP warming process and what specific phrases should I use?
Michael Ko
Co-founder & CEO, Suped
Published 15 Jul 2025
Updated 15 Aug 2025
7 min read
Navigating the IP warming process with Microsoft can be a challenging but essential step for ensuring your emails reach the inbox. Unlike some other mailbox providers, Microsoft's (formerly Hotmail, now including Outlook.com and Exchange Online Protection) systems are known for their particular scrutiny of new or recently unused IP addresses. A successful warm-up is about building trust and establishing a positive sending reputation with them.
Many email senders find themselves facing delivery challenges if they don't properly warm up their IP addresses. Issues can range from significant throttling (where your emails are delayed) to outright blocklisting (or blacklisting) if the volume increase is too rapid or content is perceived as unwanted. Effectively communicating your intentions to Microsoft's support team can make a significant difference in smoothing out this crucial phase.
Why Microsoft treats new IPs cautiously
Microsoft's email infrastructure is designed to protect its users from spam and abuse. When a new IP address begins sending email, especially in high volumes, their automated systems view it with suspicion because it lacks a established reputation. This is a common practice among major mailbox providers, but Microsoft is particularly sensitive due to the sheer volume of mail they handle daily.
The goal of IP warming is to build a positive sender reputation over time. This involves gradually increasing the volume of emails sent from a new IP address, starting with your most engaged subscribers. If you send too much email too quickly, Microsoft's filters may flag your traffic as suspicious, leading to deliverability issues.
One of the key tools for monitoring your reputation with Microsoft is their Sender Network Data Services (SNDS). Registering your IPs here provides valuable insights into your sending reputation, including spam complaints and blocklist (or blacklist) status. Regularly checking SNDS is crucial for making informed adjustments to your warming schedule.
Understanding SNDS results, particularly yellow results which indicate potential issues, allows you to adjust your sending strategy proactively. This proactive approach helps prevent major deliverability disruptions during the crucial warm-up period. Monitoring your reputation is critical, as a poor one can lead to your IP getting blocklisted.
Specific phrases to use with Microsoft support
When you encounter throttling or blocking issues during your IP warming, opening a support ticket with Microsoft can be beneficial. However, the specific phrases you use in your communication can significantly impact the response you receive and how quickly your issue is escalated and addressed. This isn't about tricking the system, but rather using the precise terminology that helps their internal processes categorize your request correctly.
You'll often receive an automated initial response. To move past this, it's advised to reiterate your request using phrases like "preemptive accommodation" or "preemptive mitigation form." These terms signal to the support staff that you are proactively trying to manage your IP reputation before or during a warm-up, rather than simply reacting to a block. Politely asking for an "escalation" can also help ensure your ticket reaches the right department.
While the forms or instructions you receive might seem unclear or even contradictory, persistence with these specific terms often leads to a more helpful interaction, eventually guiding you to a solution for adjusting throttling on your new IP. This proactive communication is a key aspect of best practices for dedicated IP warm-up.
Using the right phrases
When communicating with Microsoft support, clearly state you are warming up new dedicated IP(s). Use phrases like "preemptive accommodation" or "preemptive mitigation form" to categorize your request for special handling related to a new IP address warm-up. If you receive a generic response, politely ask for an "escalation" to ensure a human reviews your request.
This direct language helps bypass automated filters and get your case to the right deliverability team within Microsoft, potentially speeding up the warm-up process by preemptively adjusting any throttling on your new IP addresses.
Engaging with Microsoft support
To begin, you will need to open a support ticket with Microsoft. There are specific portals for this, often found within the Microsoft 365 admin center or through their sender support pages. Clearly state that you are initiating an IP warm-up process for new IP addresses.
After submitting your initial request, you might receive an automated reply. This is normal. Your next step is to respond to that automated message, re-stating your situation and explicitly using the terms we've discussed, such as asking for a "preemptive mitigation form" or "preemptive accommodation." Emphasize that the unusual traffic is due to a planned IP warm-up for a specific client or daily volume. Don't forget to include the dedicated IP addresses you are warming.
Example support ticket messageplaintext
Hello,
Thank you for looking into this. The unusual traffic is happening because we are warming up a set of dedicated IPs for our client. In order to move forward we need to increase the volume bit by bit because at the end of January this sender will be sending up to 1M emails per day to Microsoft network. Please take a second look and let me know whether we have any issues to look into with the sender.
Here are the dedicated IPs in question again: [List your IPs here]
It is also highly recommended to register your sending IP addresses with Microsoft's SNDS program and JMRP (Junk Mail Reporting Program) before you start sending. These services provide data on how Microsoft views your sending practices, which can be invaluable for diagnosing and resolving issues, especially during the warm-up phase. You may also need your Email Service Provider (ESP) to approve your SNDS request.
Patience is key. You might need to repeat your request for specific accommodation or escalation a couple of times until you get a non-automated human response. Even when you get the form, it may not be intuitive, but completing it as best you can and returning it is part of the process.
Strategic IP warming best practices
Beyond contacting support, a robust IP warm-up strategy hinges on several key practices. You should always start by sending to your most engaged subscribers who are likely to open and click your emails. This positive engagement signals to Microsoft that your emails are valued, helping to build your sender reputation.
Gradual volume increases are paramount. Avoid sudden spikes in sending volume, as these are red flags for mailbox providers, including Microsoft. A well-planned warm-up schedule will outline daily sending limits, gradually increasing over several weeks until you reach your target volume. Monitoring your deliverability closely during this time is critical.
Also, ensure your email authentication records, such as SPF, DKIM, and DMARC, are correctly configured. Microsoft heavily relies on these protocols to verify sender legitimacy. Correct authentication can significantly bolster your sender reputation and aid in the IP warming process. Misconfigurations, such as an SPF DNS timeout, can hinder deliverability even with proper warming.
Do this for success
Start small: Begin sending to your most active and engaged subscribers.
Increase gradually: Follow a structured IP warming schedule, increasing volumes slowly.
Monitor actively: Use SNDS and other analytics to track deliverability and reputation.
Authenticate properly: Ensure your SPF, DKIM, and DMARC records are correctly set up and aligned. Check out our guide to DMARC, SPF, and DKIM.
Engage support proactively: Use the precise phrases when communicating with Microsoft support.
Avoid these pitfalls
Sudden volume spikes: Sending too many emails too quickly will trigger spam filters.
Ignoring metrics: Neglecting SNDS data can lead to prolonged deliverability issues. Get help with IP warming issues.
Poor list hygiene: Sending to unengaged or old lists increases bounce and complaint rates.
Generic content: Irrelevant emails are more likely to be marked as spam, hurting reputation. This is especially true for Outlook's new sender requirements.
Ensuring a smooth IP warm-up
Successfully navigating the Microsoft IP warming process requires a combination of technical diligence, strategic sending, and precise communication. By understanding Microsoft's filtering philosophy, using the specific phrases that resonate with their support team, and adhering to best practices like gradual volume increases and active monitoring, you can significantly improve your chances of achieving optimal email deliverability.
Patience and persistence are your greatest allies. The warm-up phase can take time, and setbacks (like temporary blocklists) can occur. Consistent monitoring and the ability to adapt your strategy based on feedback from SNDS and other deliverability metrics will ensure a smooth transition to full sending volume.
Views from the trenches
Best practices
Start with very low volumes and highly engaged recipients to establish initial trust.
Segment your audience based on engagement, gradually expanding to less engaged segments.
Ensure your DNS records (SPF, DKIM, DMARC) are fully configured and valid.
Monitor your Microsoft SNDS data daily for any signs of throttling or blocking.
Proactively contact Microsoft support with specific phrases if issues arise.
Common pitfalls
Attempting to send full volume from a new IP address immediately.
Not monitoring deliverability metrics, especially bounce and complaint rates.
Sending to old, unengaged, or rented email lists during the warm-up period.
Ignoring automated responses from Microsoft support and not escalating the issue.
Failing to adapt your sending schedule based on real-time performance data.
Expert tips
If you hit a block, temporarily reduce volume significantly and then slowly increase again.
Focus on clean, compliant email content to avoid spam filters.
Consider using a dedicated IP if your sending volume is consistently high.
Patience is crucial; IP warming is a marathon, not a sprint.
For large volumes, consider staggering your IP warm-up across multiple IPs.
Marketer view
Marketer from Email Geeks says they opened a ticket with Microsoft, stating they were warming up a new IP, and that asking for a "preemptive mitigation form" was the key to getting a helpful response.
2020-09-10 - Email Geeks
Expert view
Expert from Email Geeks says that asking for "preemptive accommodation" and an "escalation" is effective, even if the initial automated responses are unhelpful. They added that the resulting form may seem nonsensical but works.
Microsoft support, clearly state you are warming up new dedicated IP(s). Use phrases like "preemptive accommodation" or "preemptive mitigation form" to categorize your request for special handling related to a new IP address warm-up. If you receive a generic response, politely ask for an "escalation" to ensure a human reviews your request.
