Why is Proofpoint blocking my Sendgrid IP address and how can I resolve it?
Michael Ko
Co-founder & CEO, Suped
Published 15 Jul 2025
Updated 19 Aug 2025
7 min read
Dealing with email blocks can be incredibly frustrating, especially when it involves a major security vendor like Proofpoint and your emails are sent through an established provider such as SendGrid. You might find yourself in a situation where your newsletters or transactional emails aren't reaching their recipients, and the problem points directly to an IP address block. Even with a dedicated IP from a reputable service, these issues can arise, causing significant headaches and impacting your communication flow.
The feeling of being stuck in the middle, with users complaining and no clear path to resolution, is something many email senders experience. Understanding why Proofpoint might be blocking your specific SendGrid IP address, and knowing the steps to take for resolution, is crucial for restoring your email deliverability.
Why Proofpoint blocks SendGrid IP addresses
When your SendGrid IP address (even a dedicated one) gets blacklisted or blocklisted by Proofpoint, it is often due to a reputation issue. Proofpoint maintains its own proprietary blocklists and uses dynamic reputation systems. These systems assess the sending behavior from an IP, and if they detect patterns associated with spam, phishing, or other malicious activities, that IP can be added to their internal blocklist, preventing your emails from reaching recipients protected by Proofpoint.
A key factor is that even a dedicated IP from a large Email Service Provider (ESP) like SendGrid might carry reputational baggage from previous users. IP addresses are recycled, and if the previous sender on your now-dedicated IP had poor sending practices, that negative history can persist for a time. Proofpoint's system might also consider the reputation of the broader Autonomous System Number (ASN) that the IP belongs to, which means even if your specific IP is clean, the general reputation of the network it sits on could influence its decision.
Additionally, the content of your emails can play a role. If your messages contain characteristics that Proofpoint's filters identify as spam, even if your IP is generally clean, it can trigger blocks. This includes suspicious links, overly promotional language, or elements commonly found in phishing attempts. It's not just about the IP, but also what you're sending from it.
Immediate steps to resolve the block
The first step in resolving a Proofpoint block is to confirm the listing and gather all necessary information. You'll need the exact IP address that is being blocked and any bounce messages or error codes you receive. These often provide clues about why the block occurred.
You can use Proofpoint's own IP lookup tool to check the status of your IP. If it confirms a listing, the next critical step is to submit a delisting request. Proofpoint typically provides a web form for this, and they also have a postmaster email address (postmaster@proofpoint.com) that is often responsive. When submitting your request, be sure to include all relevant details, such as the blocked IP, your domain, and a brief explanation of the issue.
Patience is key during this process. Responses can sometimes take a few days, and follow-ups might be necessary. While you await a response, focus on improving your sending practices to demonstrate that your IP deserves to be delisted. You can also refer to how to contact Proofpoint about IP blocks for more detailed guidance.
Preventing future blocklists and maintaining reputation
Causes of IP blocklist
Poor sending reputation: The IP has been used by spammers in the past or has recently sent large volumes of unengaged emails.
Spam complaints: High rates of users marking your emails as spam can quickly damage IP reputation.
Invalid email addresses: Sending to a high percentage of non-existent or inactive email addresses (spam traps) hurts your sender score.
Shared IP issues: Even with a dedicated IP, if it's part of a larger network (like an ASN) with poor overall reputation, it can be impacted. Some providers block broad IP ranges.
Lack of authentication: Absence or misconfiguration of SPF, DKIM, and DMARC records can signal untrustworthiness to email security gateways like Proofpoint.
To prevent future blocks and maintain healthy email deliverability, you need to implement robust sender reputation management practices. One critical aspect is proper IP warming for new or re-assigned IP addresses. This involves gradually increasing your sending volume over time, allowing mailbox providers to assess your legitimate sending patterns and build a positive reputation.
List hygiene is another paramount factor. Regularly cleaning your email lists to remove inactive, invalid, or unengaged subscribers will significantly reduce bounce rates and minimize the chances of hitting spam traps. Spam traps are email addresses specifically set up to catch spammers, and hitting them can severely damage your reputation and lead to blacklistings (or blocklistings).
Furthermore, ensuring your email authentication protocols are correctly set up is vital. This includes SPF, DKIM, and DMARC. These protocols verify that your emails are legitimate and originate from your domain, building trust with receiving servers. While DMARC itself doesn't directly influence IP reputation for initial connection-level blocks, its presence signals a commitment to email security and can indirectly contribute to overall domain and sending identity trustworthiness.
Proactive vs. reactive measures
Proactive measures
Before you encounter a block, setting up continuous blocklist monitoring is a crucial step. This allows you to be alerted immediately if your IP or domain appears on any major blocklists or blacklists, enabling a swift response. Early detection is key to minimizing the impact on your email deliverability.
Monitor sending metrics: Keep a close eye on your bounce rates, spam complaint rates, and engagement metrics within your ESP dashboard. Proactive monitoring helps identify issues before they escalate.
Implement strong authentication: Ensure your SPF, DKIM, and DMARC records are correctly configured and aligned.
Reactive measures
When a block occurs, swift action is required. Your focus should be on isolating the cause, rectifying any underlying issues, and then diligently pursuing delisting requests with the blocking entity, in this case, Proofpoint.
Review email content: Analyze recent campaigns for potential spam triggers or suspicious elements that might have led to the block.
Segment audiences: Consider segmenting your audience and sending to highly engaged users first to rebuild reputation.
Ensuring long-term deliverability
Navigating IP blocklistings, especially with a sophisticated system like Proofpoint, requires a multi-faceted approach. It's not just about getting off a blocklist once, but about establishing and maintaining a robust sending reputation. This involves consistent monitoring, adherence to best practices, and a proactive stance on email authentication and list management.
Understanding that email deliverability is an ongoing effort, not a one-time fix, is crucial. By diligently applying these strategies, you can minimize the risk of future blocks and ensure your messages consistently reach your recipients' inboxes, rather than being caught in a spam filter.
Views from the trenches
Best practices
Maintain meticulous list hygiene to avoid inactive or invalid addresses that lead to blocks.
Gradually increase email volume for new IPs to build a positive sending reputation over time.
Consistently monitor your IP and domain health using reputable blocklist checking tools.
Common pitfalls
Assuming a dedicated IP is automatically clean; it can carry prior reputational baggage.
Neglecting to implement DMARC, SPF, and DKIM, which are crucial for sender identity verification.
Not regularly auditing email content for potential spam triggers or aggressive marketing language.
Expert tips
Consider the overall reputation of your ESP's network, not just your dedicated IP.
While DMARC itself doesn't cause or fix IP blocks, it's essential for domain reputation.
Patience is key; delisting requests can take time to be processed and acknowledged.
Expert view
Expert from Email Geeks says not all ESPs maintain the same level of quality and reputation over time.
2023-03-29 - Email Geeks
Marketer view
Marketer from Email Geeks says SendGrid's reputation calculations and reporting may not always be accurate.
2023-03-29 - Email Geeks
Key takeaways for reliable email delivery
Resolving a Proofpoint block on your SendGrid IP address requires a combination of immediate troubleshooting and long-term reputation management. By promptly addressing the block, actively engaging with Proofpoint for delisting, and diligently implementing best practices such as IP warming and strong authentication, you can overcome these deliverability challenges.
Remember, email deliverability is a continuous journey. By staying vigilant and maintaining excellent sending hygiene, you can ensure your emails consistently reach their intended recipients, bypassing the filters of even the most stringent security gateways.
SendGrid might carry reputational baggage from previous users. IP addresses are recycled, and if the previous sender on your now-dedicated IP had poor sending practices, that negative history can persist for a time. Proofpoint's system might also consider the reputation of the broader Autonomous System Number (ASN) that the IP belongs to, which means even if your specific IP is clean, the general reputation of the network it sits on could influence its decision.
