How to handle SendGrid shared IP blacklisting with low email volume?
Michael Ko
Co-founder & CEO, Suped
Published 2 Jun 2025
Updated 17 Aug 2025
7 min read
Dealing with a SendGrid shared IP address being added to a blacklist (or blocklist) can be incredibly frustrating, especially when you are a low-volume sender. It feels unfair when your legitimate emails are blocked because of the actions of others in the same shared IP pool. You might be sending just a handful of emails per day, but if a high-volume spammer shares your IP, your deliverability can tank without warning.
The common advice to get a dedicated IP often doesn't make sense for low email volumes, as it is both costly and introduces new challenges like IP warm-up. So, what are your options when you are caught in this bind? We will explore how to diagnose the issue, understand why it happens, and outline practical strategies to ensure your emails reach the inbox despite shared IP blocklisting.
Shared IP addresses are a common offering from Email Service Providers (ESPs) like SendGrid, particularly for free or low-cost plans. The idea is that the collective sending volume of many users on the same IP builds a strong sender reputation. However, this also means that the reputation of the IP is an aggregate of all users. If even a few bad actors (spammers) are on the same shared IP, it can quickly lead to that IP being listed on a blocklist or blacklist by Internet Service Providers (ISPs) and anti-spam organizations, impacting everyone sharing it.
For low-volume senders, this poses a significant problem. You lack the volume to significantly influence the IP's overall reputation yourself. Your handful of legitimate emails might be drowned out by a surge of spam from another user, causing the IP to be blocklisted. When an IP is listed, receiving mail servers might issue a 550 error, indicating that the message was rejected due to a policy reason, such as a poor IP reputation. Specific blocklists (or blacklists) like Spamcop.net, known for being quite aggressive, can be particularly problematic.
The tricky part is that a generic 550 error does not always explicitly state that the IP is blacklisted. The exact rejection message, including the error code and any accompanying text, is crucial for understanding the specific reason for blocking. Without this detail, diagnosing whether it is indeed an IP blocklist (or blacklist) issue or something else, like content or domain reputation, becomes challenging. While you can check your IP against various blocklists using a blocklist checker, a listing does not always mean it is the reason for a specific rejection. The recipient's ISP may not use that particular blocklist.
Diagnosing shared IP issues
The first step in resolving shared IP blocklisting for low-volume sending is accurate diagnosis. You need to verify that your emails are indeed being blocked due to the shared IP's reputation and not other factors, such as your domain's authentication or content. Accessing the full bounce message from SendGrid is essential, as it often contains specific details about why the email was rejected.
Decoding bounce messages
When an email bounces, the error message from the receiving server is the most direct indicator of the problem. A common temporary error code is 4xx, while a permanent rejection is indicated by a 5xx code. For IP blocklisting, you will often see a 550 error combined with text that references spam, blacklists, or IP reputation issues. However, 550 is a broad category, so the additional text is critical. You can also refer to SendGrid's official guide for understanding bounce types.
Example bounce messages for IP blocklisting
550 5.7.1 Service unavailable; Client host [X.X.X.X] blocked using SBL.
550 5.7.1 This message was blocked because the sending IP is on a blacklist.
If the bounce messages clearly indicate an IP blocklist (or blacklist) issue, especially from a specific ISP or domain, then you can be more certain of the root cause. This information will guide your next steps, whether it is considering a different ESP or evaluating your current SendGrid plan.
Strategies for low volume senders
For low-volume senders experiencing shared IP blocklisting, there are a few primary strategies. The most direct approach is to consider switching to an ESP known for cleaner shared IP pools or upgrading your SendGrid plan to access a better pool. Another option, though less scalable, is to communicate with recipients whose domains are specifically blocking your emails due to the blocklist.
Challenges
Reputation volatility: Your sender reputation is tied to other users, making it vulnerable to their poor sending practices. This can lead to your emails being affected by someone else's missteps, an issue common with shared IP reputation problems.
Limited control: You have no direct control over the IP's overall health or how quickly it is delisted from a blocklist. What happens when your IP is blocklisted?
Monitoring challenges: You must rely on your ESP's internal monitoring and management of the shared IP. You may not get granular insights into why the IP is struggling.
Free tiers on many ESPs, including SendGrid, often place users in shared IP pools that are more prone to blocklisting due to higher rates of abuse from throwaway accounts. This means you might be in a less desirable sending environment.
Dedicated IP considerations
Cost prohibitive: Dedicated IPs usually come with a significant monthly fee that often outweighs the benefits for low-volume senders. This is particularly true if you are looking for free options, or something in the range of $20-30 per month.
IP warm-up: Even with low volume, a dedicated IP requires a careful IP warm-up process to build a reputation. This can be challenging with inconsistent or very low daily sends.
Reputation responsibility: You are solely responsible for your IP's reputation, meaning any sending errors on your part can directly harm your deliverability, as discussed in our article, is a dedicated IP address suitable for low volume?
Given that a dedicated IP is often not viable for low-volume sending, switching to an alternative ESP or a paid SendGrid plan (which often offers cleaner shared pools) might be the most effective solution. Different ESPs have varying approaches to managing shared IP pools, and some maintain a stricter stance on abuse, leading to better overall deliverability. Look for providers that prioritize sender hygiene on their shared IPs.
Provider
Cost (approx.)
Shared IP Reputation
Notes
Postmark
$15/month
Stellar
Known for high deliverability, strict on abuse.
Amazon SES
Cheaper, free for low volumes
Often better
Requires AWS setup, good for developers. They care about abuse.
ElasticEmail
Competitive pricing
Good experience reported
Consider their pricing tiers for your specific volume needs.
If the problem is limited to a small group of recipients or specific domains that use aggressive blocklists (like Spamcop), you might consider an interpersonal approach. This involves directly contacting those recipients via alternative means and explaining that their ISP is blocking your legitimate emails due to a shared IP blocklist. This can be a short-term solution to ensure critical communications go through while you work on a more permanent fix, though it is not scalable for a large recipient base.
Long-term deliverability
Even when using shared IPs, maintaining strong sending practices is paramount. Your domain's reputation plays a critical role in deliverability, often more so than the IP address, especially with modern ISP filtering algorithms. Ensuring your emails are properly authenticated and that your sending content is clean and engaging will go a long way in mitigating the impact of shared IP issues.
Implement strong email authentication protocols such as SPF, DKIM, and DMARC. These protocols prove that your emails are legitimate and that you own the sending domain, building trust with receiving mail servers. A well-configured DMARC record, for instance, helps ISPs understand your sending intentions and can protect your domain from impersonation, even if the shared IP has a questionable reputation. This is a fundamental step in boosting your email deliverability rates.
Content quality: Ensure your email content is valuable, relevant, and free of spam triggers. Even plain text emails can be flagged if content is suspicious.
List hygiene: Regularly clean your email lists to remove inactive or invalid addresses, reducing bounce rates and the risk of hitting spam traps. This also contributes to fixing why your emails go to spam.
While you cannot control the actions of other senders on a shared IP, focusing on your own domain's reputation and compliance with email best practices can significantly improve your deliverability. A robust domain reputation can sometimes override issues with a shared IP, especially for transactional or highly engaged emails. Regularly monitor your deliverability and adjust your strategy as needed.
Views from the trenches
Best practices
Opt for an ESP with a reputation for cleaner shared IP pools, even if it means a small monthly fee.
Always include complete bounce messages in support tickets to your ESP for accurate diagnosis.
Thoroughly authenticate your domain with SPF, DKIM, and DMARC, as this builds trust with ISPs.
Communicate directly with recipients from domains that are consistently blocking your emails.
Regularly monitor your domain's reputation using tools like Google Postmaster Tools for insights.
Common pitfalls
Assuming all 550 errors are due to IP blacklisting without checking the full bounce message.
Sticking with free shared IP plans when they consistently cause deliverability issues.
Migrating to a dedicated IP for very low email volumes, leading to new warm-up challenges.
Neglecting domain authentication, which can lead to rejections even with a clean IP.
Failing to clean your email lists, increasing bounce rates and spam trap hits over time.
Expert tips
If your backend permits it, consider trying a few different ESPs' free or low-cost plans to see which offers the best shared IP deliverability for your specific needs.
For extremely low volume (e.g., a few emails per day), using a standard Gmail or Outlook account's outbound SMTP can sometimes provide better deliverability than a problematic ESP shared IP.
Be aware that some ESPs might retry sending after a 550 error, which can further degrade their shared IP's reputation, potentially impacting you.
The paid tiers of ESPs often have access to better-managed shared IP pools, which can be a worthy investment for reliable delivery.
Don't solely rely on general blacklist checks; understand which specific lists recipient ISPs use to determine if a blocklist hit is truly impacting your emails.
Expert view
Expert from Email Geeks says the exact rejection messages and recipient domain are crucial for understanding why emails are being blocked.
2024-05-28 - Email Geeks
Expert view
Expert from Email Geeks says if the problem is solely from SendGrid's shared pool IPs, the main options are to switch to a different, better provider or upgrade to a paid SendGrid plan for a less problematic pool.
2024-05-28 - Email Geeks
Moving forward
Navigating SendGrid shared IP blocklisting with low email volume can be a persistent challenge. The core issue often stems from the inherent nature of shared IPs, where your deliverability is influenced by others in the same pool. While a dedicated IP might seem like an obvious solution, for low-volume senders, it introduces unnecessary cost and the complexities of IP warm-up without sufficient sending volume.
The most effective path forward typically involves a strategic shift: either upgrading your SendGrid plan to access cleaner shared IP pools or exploring alternative ESPs like Postmark, Amazon SES, or ElasticEmail, which may offer better shared IP reputations for your volume. Coupled with diligent domain authentication (SPF, DKIM, DMARC) and consistent list hygiene, you can significantly improve your email deliverability and ensure your crucial messages reach their intended recipients.
shared IP address being added to a blacklist (or blocklist) can be incredibly frustrating, especially when you are a low-volume sender. It feels unfair when your legitimate emails are blocked because of the actions of others in the same shared IP pool. You might be sending just a handful of emails per day, but if a high-volume spammer shares your IP, your deliverability can tank without warning.
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