How can I improve email deliverability on a shared IP for marketing automation emails like abandoned carts?
Michael Ko
Co-founder & CEO, Suped
Published 8 Jul 2025
Updated 17 Aug 2025
8 min read
Improving email deliverability on a shared IP, especially for marketing automation emails like abandoned cart reminders, can be a complex challenge. Many businesses, particularly those with lower sending volumes, rely on shared IP addresses provided by their email service providers (ESPs). While shared IPs offer benefits by distributing the sending reputation across many users, they also tie your deliverability to the sending habits of others on the same IP pool. This can be frustrating when your messages aren't reaching the inbox, even with correct authentication setup.
You might assume that if your SPF, DKIM, and DMARC records are perfectly configured, your emails should land in the inbox. However, deliverability is influenced by much more than just technical authentication. For marketing automation, the recipient's engagement with your emails plays a critical role, arguably even more so than the specific IP address you're sending from.
The good news is that by focusing on several key areas, you can significantly improve your inbox placement rates, even when operating on a shared IP address. It's about building and maintaining a strong sender reputation through strategic content, list management, and consistent monitoring.
The nuances of shared IP deliverability
Shared IP addresses are common among email service providers (ESPs) such as Klaviyo or Brevo. These pools allow multiple senders to use the same set of IP addresses, which is particularly beneficial for small to medium-sized businesses or those with inconsistent sending volumes. It prevents individual senders from needing to warm up a dedicated IP address, leveraging the collective reputation of the entire shared pool. This means a new sender can initially benefit from the ESP's established sender reputation.
However, the downside is that your sending behavior is intertwined with that of other users on the same shared IP. If another sender in the pool engages in poor practices, like sending spam or to unengaged lists, it can negatively impact the reputation of the entire IP, including your deliverability. While proper technical setup (like SPF, DKIM, and DMARC) is crucial for identifying your domain as legitimate, it doesn't entirely insulate you from a shared IP's overall reputation.
Mailbox providers (ISPs) increasingly prioritize domain reputation over IP reputation, especially for marketing emails. This means that while the shared IP provides a base level of trust, your specific domain's reputation, built on recipient engagement, is what truly determines inbox placement. Even a minor dip in engagement can lead to emails landing in the spam folder, regardless of the shared IP's general standing.
Dedicated IP
You control the entire IP reputation, allowing for precise management. Requires a high and consistent sending volume to maintain a good reputation. Ideal for large enterprises with steady email campaigns.
Volume control: Requires a minimum of 3,000 emails per day for effective warming and maintenance.
Warming process: Essential to gradually increase sending volume over weeks or months.
Shared IP
Your reputation is influenced by other senders on the same IP. Suitable for lower or inconsistent sending volumes, as the ESP manages the overall IP reputation. Common for new businesses or those without high-volume needs.
Volume control: No specific minimum volume required, suitable for small lists.
Warming process: The ESP manages warming for the shared pool.
Cultivating sender reputation beyond the IP
While your IP address has some impact, particularly on shared pools, your domain reputation is the single most important factor for deliverability. Mailbox providers (ISPs like Google and Yahoo) primarily assess your domain's sending history and engagement metrics to decide where your emails land. This is why even with excellent authentication on a shared IP, you might still see low inbox rates.
Engagement is key. Open rates, click-through rates, replies, and how often recipients move your emails from spam to inbox all signal to ISPs that your emails are wanted. Conversely, low engagement, high unsubscribe rates, or spam complaints will severely damage your domain's reputation. This is especially true for new senders with low volumes, as there isn't enough positive history to outweigh any negative signals.
To improve your email and domain reputation, consider diversifying your email content beyond just transactional or abandoned cart messages. While abandoned carts are valuable, they might not generate the same level of positive engagement as a welcome series, a promotional offer, or a regular newsletter that genuinely interests your subscribers. By sending a variety of emails that consistently get opened and clicked, you actively build a positive sending history for your domain.
Strategic approaches for abandoned cart emails
Abandoned cart emails are undeniably effective for recovery, but their deliverability hinges on how they are perceived by recipients and ISPs. If these are the only emails you're sending, particularly with a small and new list, you might inadvertently be signaling low engagement to mailbox providers. The key is to ensure these emails are genuinely anticipated and valued, even if they're automated.
Personalize and add value to abandoned cart emails. Don't just remind them about the cart. Offer helpful tips related to the products, suggest alternatives, or provide excellent customer service contact information. Consider the timing of these emails as well, as sending too many too quickly can lead to irritation and spam complaints. A single, well-crafted reminder can be more effective than multiple aggressive ones.
For new senders with limited volume, it might be beneficial to first build a positive domain reputation with other types of emails that are more likely to generate high engagement. This could include welcome series emails, exclusive offers for new subscribers, or content-rich newsletters. Once your domain's reputation is robust, your abandoned cart emails will have a much better chance of reaching the inbox. This initial domain warm-up will lay a solid foundation.
Element
Effective strategy
Ineffective strategy
Content
Personalized, value-driven messages with helpful product context or customer support options.
Generic, hard-sell reminders lacking personalization or additional value.
Timing
Strategically timed, limited follow-ups, perhaps with a clear call-to-action.
Excessive or immediate follow-ups that feel intrusive or desperate.
Goal
To genuinely assist the customer in completing their purchase, building trust.
Solely focused on conversion at all costs, ignoring user experience.
Essential technical and hygiene practices
Even on a shared IP, strong technical foundations are non-negotiable for email deliverability. Ensuring your SPF, DKIM, and DMARC records are correctly set up is fundamental. These authentication protocols verify that your emails are legitimate and prevent spoofing, which is a major factor in avoiding spam folders. Many ISPs now require these for good deliverability, especially after recent updates from Google and Yahoo. Consider a DMARC p=none policy as a starting point if you haven't implemented it fully.
List hygiene is equally important. Even with a small list, regularly cleaning it to remove inactive or invalid addresses prevents bounces and spam traps. Using a double opt-in process, where subscribers confirm their email address after signing up, ensures that everyone on your list genuinely wants to receive your emails. This dramatically reduces complaints and boosts engagement, signaling to ISPs that your emails are welcome.
Focus on list quality
Prioritize acquiring high-quality subscribers who are genuinely interested in your content. Even a small, highly engaged list will perform better than a large, unengaged one.
Implement double opt-in: This verifies subscriber intent and reduces spam complaints.
Regularly clean your list: Remove inactive users and hard bounces to maintain good sending hygiene.
Finally, monitor your deliverability closely. Pay attention to your open rates, click-through rates, and especially your spam complaint rates through tools like Google Postmaster Tools and your ESP's analytics. A complaint rate exceeding 0.10% can be detrimental. Use a blocklist checker to see if your IP or domain (or the shared IP pool) ends up on any blacklists. Consistent monitoring allows you to identify and address issues promptly.
Views from the trenches
Best practices
Actively encourage engagement by sending diverse, valuable content, not just abandoned cart reminders.
Segment your audience and tailor messages to their specific interests and behaviors.
Maintain a clean email list by regularly removing inactive or invalid addresses.
Common pitfalls
Relying solely on shared IP reputation without building your own domain's credibility.
Sending high volumes of emails too quickly, especially for new sender domains.
Ignoring low open rates or high spam complaints, which degrade sender reputation.
Expert tips
Your domain's reputation is paramount, even on a shared IP, so prioritize engagement.
For low sending volumes, shared IPs are often more appropriate than dedicated ones.
Focus on the recipient's desire for your emails, not just technical compliance.
Marketer view
A marketer from Email Geeks says if you're using a provider and have custom sending and link tracking domains set up, your deliverability issues are likely due to your own sending practices rather than the shared IP pool itself. They noted that their previous client's shared IP seemed to have lower reputation, and the provider suggested a dedicated IP without offering to move them to a better pool.
2024-02-11 - Email Geeks
Marketer view
A marketer from Email Geeks observed that if a platform like Klaviyo truly had poor deliverability, there would be widespread complaints. They advised troubleshooting one's own traffic first by checking for explicit permission, recipient desire for emails, and how mail and audience differ between sending platforms.
2024-02-12 - Email Geeks
Final thoughts on shared IP deliverability
Improving email deliverability on a shared IP for marketing automation, particularly abandoned cart emails, requires a holistic approach. While shared IPs offer a convenient starting point for lower volume senders, your ultimate success hinges on your domain's reputation, which is primarily driven by recipient engagement.
Focus on building a highly engaged list, send content that your subscribers genuinely want to receive, and maintain impeccable list hygiene. Ensure all your email authentication records are correctly configured. By proactively managing these factors, you can significantly enhance your inbox placement and maximize the effectiveness of your abandoned cart campaigns, even in a shared IP environment.
Klaviyo or Brevo. These pools allow multiple senders to use the same set of IP addresses, which is particularly beneficial for small to medium-sized businesses or those with inconsistent sending volumes. It prevents individual senders from needing to warm up a dedicated IP address, leveraging the collective reputation of the entire shared pool. This means a new sender can initially benefit from the ESP's established sender reputation.
Google and 
Yahoo) primarily assess your domain's sending history and engagement metrics to decide where your emails land. This is why even with excellent authentication on a shared IP, you might still see low inbox rates.
