How should I warm up my IP address for B2B email sends to avoid Proofpoint blocks?
Michael Ko
Co-founder & CEO, Suped
Published 5 Jun 2025
Updated 16 Aug 2025
8 min read
Warming up a new IP address is a critical step for any email sender, but it presents unique challenges when sending B2B emails, especially when dealing with advanced security gateways like Proofpoint. Unlike consumer ISPs that primarily rely on engagement metrics from vast user bases, B2B email environments often involve more stringent filtering by corporate security solutions.
My goal is to guide you through an effective IP warming strategy tailored for B2B sending, focusing on how to establish a strong sending reputation that bypasses potential Proofpoint blocks. The core principle remains consistent: start with low volumes and gradually increase them. However, the nuances for B2B, particularly with security vendors, require a more strategic approach.
Understanding what Proofpoint looks for is key. They often prioritize real-time threat intelligence and user feedback, alongside standard authentication protocols. This means a good IP warming plan for B2B isn't just about volume, but also about the quality and relevance of your emails from day one.
A common mistake I've observed is trying to rush the process, leading to sudden spikes in volume that can trigger security filters. Even if your ultimate send frequency will be lower, a consistent daily increase during warming is generally safer than large jumps followed by lulls, especially when a deadline looms. This approach helps build trust with receiving mail servers over time.
Understanding IP warming for B2B email
IP warming (or IP ramp-up) is the process of gradually increasing the volume of email sent from a new IP address. This helps internet service providers (ISPs) and email security gateways recognize your IP as a legitimate sender. For B2B email, the stakes are often higher due to the critical nature of these communications and the sophisticated filters employed by corporate networks.
Unlike consumer ISPs that track a wide range of user interactions such as opens, clicks, and spam complaints across millions of users, B2B filters, including Proofpoint, are highly sensitive to sudden changes in sending patterns or suspicious content. They prioritize preventing malware, phishing, and other advanced threats, meaning a new IP with sudden high volume can be flagged quickly, even if the content is benign. The general advice for warming up an IP address still applies, but with an added layer of scrutiny.
For B2B environments, establishing a positive sender reputation is less about accumulating massive engagement signals and more about demonstrating consistent, legitimate sending behavior. This includes maintaining clean lists, sending highly relevant content, and ensuring your email authentication is impeccable. A sudden influx of emails, even to a segmented list, can appear abnormal and lead to temporary blocks or greylisting.
The key takeaway for B2B is that reputation is built on trust and predictability. Any behavior that deviates significantly from a predictable, positive sending pattern can raise red flags. This is particularly true for larger organizations that rely on robust email security solutions to protect their employees from threats.
Proofpoint and B2B email security
Proofpoint is a leading cybersecurity company that provides advanced threat protection, compliance, and email security solutions. Their email gateways are widely used by businesses to filter out spam, phishing attacks, malware, and other malicious content. When your emails are blocked by Proofpoint, it often indicates a perceived threat or a significant deviation from expected sender behavior, rather than solely a lack of IP reputation.
A common bounce message from Proofpoint might be "5.3.2 (system not accepting network messages) Blocked". This typically means your IP or domain has been flagged, often due to a poor sender score or inclusion on a private blocklist (also known as a blacklist). Proofpoint heavily utilizes a feedback loop system, where recipients' actions (like marking emails as spam) contribute significantly to your sender score. Therefore, high spam complaints or low engagement, even from a small subset of your list, can quickly lead to blocks.
It's important to understand that removing your IP from their blocklist once is not a permanent solution if the underlying sending behavior that caused the initial block persists. They will re-flag it if they detect continued suspicious activity. This highlights the importance of not just warming up the IP, but also maintaining excellent sending hygiene from the outset.
Addressing Proofpoint blocks
If you find your IP blocklisted by Proofpoint, direct communication is often the most effective route. You can contact them via email to inquire about the specific reasons for the block and the steps needed for delisting. Always be prepared to demonstrate that you adhere to email sending best practices.
The ideal IP warming schedule for B2B often involves a phased approach that prioritizes sending to your most engaged subscribers first. This helps to generate positive engagement signals early on. The goal is to build a consistent sending pattern that aligns with your future regular volume without alarming email security systems.
While it might be tempting to send daily during warming, even if your normal schedule is bi-weekly, consider the long-term pattern you want to establish. ISPs and security gateways use machine learning to detect anomalies. A drastic drop in frequency after a rapid warm-up could be seen as unusual behavior. Generally, it's best to start as you mean to go on, adjusting daily volume but keeping frequency somewhat consistent with your ultimate sending cadence.
For B2B sends where weekend engagement is low, it’s advisable to maintain a weekday-only sending schedule during warm-up if that mirrors your eventual strategy. However, be cautious about significant volume increases after weekend breaks, as this can trigger blocklists. A gradual daily increase, even with weekend pauses, needs careful monitoring.
A typical warm-up can take 15 to 60 days, depending on your target volume. For large sends, such as 450,000 subscribers bi-weekly, a comprehensive approach is required. For more general guidance, this Twilio SendGrid resource on IP warm-up can provide additional insights.
Day Range
Daily Volume (Approx.)
Audience Focus
Days 1-3
2,000-5,000
Most engaged subscribers: Recent opens/clicks.
Days 4-7
5,000-10,000
Engaged subscribers: Active within last 90 days.
Week 2
10,000-25,000
Moderately engaged: Active within last 6 months.
Week 3-4
25,000-50,000+
All active subscribers: Gradually include less engaged segments.
Beyond Week 4
Full volume
Maintain engagement: Regularly clean your list and monitor performance.
Key factors in avoiding Proofpoint blocks
Beyond just volume, several critical factors influence your sender reputation and how Proofpoint (and other security gateways) will treat your emails.
Email authentication
Ensuring your emails are properly authenticated with SPF, DKIM, and DMARC is non-negotiable for B2B sending. These protocols verify your identity as a sender and significantly impact deliverability. Proofpoint will heavily scrutinize emails that fail these checks. A solid authentication setup builds trust from the very first send.
Content quality and engagement
For B2B emails, content relevance and engagement are paramount. Sending valuable, anticipated content to a highly segmented and engaged audience during warming is crucial. This generates positive feedback, reducing spam complaints and fostering a good sender reputation. Avoid sending generic or unsolicited content, especially during the initial warm-up phase.
List hygiene and spam traps
Clean your email lists rigorously before starting the warm-up process. Removing old, inactive, or invalid addresses is critical to avoid hitting spam traps or generating excessive bounces. Spam traps are email addresses used to identify unsolicited senders and hitting them can severely damage your reputation, leading to immediate blocklisting.
Segment your audience: Start with your most engaged B2B subscribers for initial sends.
Monitor deliverability metrics daily: Keep an eye on bounces, complaints, and engagement rates.
Provide clear unsubscribe options: Make it easy for recipients to opt out, reducing spam complaints.
Align content with expectations: Send relevant, valuable B2B content that your subscribers anticipate.
What to avoid
Sudden volume spikes: Do not drastically increase sending volume overnight or after a break.
Sending to unengaged lists: Avoid old, purchased, or unverified lists during warm-up.
Ignoring bounce messages: Analyze feedback from blocklists (e.g., Proofpoint) and adjust strategy.
Sending too frequently: If your normal cadence is weekly, avoid daily sends unless under a tight deadline and managed carefully.
Using misleading subject lines: Avoid anything that could be perceived as spammy or deceptive.
Views from the trenches
Best practices
Always segment your list, starting with the most engaged contacts during the initial warm-up phase to ensure positive reception.
Maintain consistent sending patterns throughout the warm-up period to build predictable reputation signals with mail providers.
Prioritize email authentication (SPF, DKIM, DMARC) from day one to establish trust and avoid initial blocks.
Monitor your deliverability metrics closely, looking for early signs of issues like increased bounces or complaints.
Clean your email list thoroughly to remove inactive or invalid addresses, which can trigger spam traps and lower your reputation.
Common pitfalls
Drastically increasing email volume too quickly can overwhelm mail servers and lead to immediate blacklisting.
Sending to unengaged or old lists, which are more likely to contain spam traps or generate complaints.
Ignoring bounce codes or deliverability reports, missing critical signals that indicate reputation issues.
Trying to warm up too fast under a tight deadline without carefully managing volume and list quality.
Neglecting proper email authentication, which makes your emails appear suspicious to security filters.
Expert tips
For B2B, content relevance and high recipient engagement are often more influential than raw sending volume.
If facing a tight deadline, it might be necessary to send daily during warm-up, but ensure the list quality is exceptional.
Remember that B2B filters like Proofpoint place a strong emphasis on real-time feedback and threat intelligence.
Don't just remove your IP from a blocklist; identify and fix the underlying issue that caused the block in the first place.
A gradual ramp-up in volume is always recommended, even if it feels slow, to build a stable and trusted sending reputation.
Expert view
Expert from Email Geeks says start slow with your most engaged audience. This approach trains mailbox providers to expect your emails while showing recipients want them.
2021-04-06 - Email Geeks
Expert view
Expert from Email Geeks says establishing your IP's pattern during warming means doing something that isn't your normal pattern neither hurts nor helps.
2021-04-06 - Email Geeks
Sustaining B2B email deliverability
Successfully warming up your IP address for B2B email sends, particularly to avoid Proofpoint blocks, requires a meticulous and disciplined approach. It's not just about hitting volume targets, but about building and maintaining a stellar sender reputation through consistent best practices.
Prioritize sending to your most engaged B2B subscribers first, maintain impeccable list hygiene, and ensure all your email authentication protocols (SPF, DKIM, DMARC) are correctly configured. By doing so, you'll establish a trustworthy sending pattern that minimizes the risk of being blocklisted and maximizes your email deliverability to critical business contacts. Remember, establishing a good sender reputation is an ongoing process, not a one-time task.
Proofpoint. Unlike consumer ISPs that primarily rely on engagement metrics from vast user bases, B2B email environments often involve more stringent filtering by corporate security solutions.
