What to do when SFMC shared IP reputation tanks due to other senders?
Matthew Whittaker
Co-founder & CTO, Suped
Published 27 May 2025
Updated 17 Aug 2025
8 min read
It's incredibly frustrating when your meticulously nurtured email program suddenly hits a wall, not because of your own sending practices, but due to the actions of others sharing your email service provider's (ESP) IP addresses. You've diligently warmed up your domain, maintained excellent engagement metrics, and then, without warning, your emails are blocked by major providers like Yahoo and Microsoft, or delayed by Gmail.
This scenario is particularly common with shared IP pools, where a sudden surge in volume or poor sending by other clients can drastically tank the collective IP reputation. I've heard countless stories where senders, despite their best efforts, experience a sharp decline in deliverability, seeing sender scores plummet overnight. It feels unfair, especially when you've invested in a premium package that includes a dedicated IP, but your current volume doesn't yet meet the typical threshold for using it.
Navigating this challenge requires a strategic approach. While the immediate instinct might be frustration, understanding the underlying dynamics of shared IP reputation and knowing how to engage with your ESP's support team is crucial. This article will explore why shared IP reputation tanks, what immediate steps you can take, and how to plan for better long-term deliverability.
The challenge of shared IP reputation
Shared IPs are a cost-effective solution for many senders, but they come with inherent risks. When you send emails from a shared IP address, your sending reputation becomes intertwined with that of every other sender utilizing the same IP. This means that a single bad actor (or multiple ones) sending spam, hitting spam traps, or generating high complaint rates can swiftly degrade the IP's overall standing. Mailbox providers (ISPs) then view all traffic from that IP with suspicion, leading to blocks or delays for legitimate senders.
Identifying the impact often starts with observing bounce rates or delays, particularly from major B2C ISPs. Tools like SenderScore can offer insights into the reputation of specific IP addresses, revealing sudden drops in score that correlate with increased volume from unknown sources. While these tools provide a general overview, gaining detailed insights into which specific senders are causing issues on a shared IP (or even which specific IPs in a pool are problematic) is typically impossible due to ESP privacy policies.
For Salesforce Marketing Cloud (SFMC) users, the challenge is exacerbated by the platform's scale and the diverse nature of its clientele. SFMC uses shared IP pools for many accounts, and while they have policies regarding acceptable use, maintaining consistent compliance across a vast user base can be difficult. This can lead to situations where even well-behaved senders find their deliverability compromised. It's important to understand that your domain's reputation is distinct from the IP reputation, and it can eventually help to mitigate some of the damage, but it takes time.
Immediate steps when reputation tanks
When your deliverability suddenly declines on a shared SFMC IP, the first and most critical step is to engage immediately with Salesforce support. Clearly articulate the issue, providing specific dates, times, and observed impacts such as increased bounce codes (e.g., Gmail 550 5.7.1 blocks) or significant delays. Reference any data you have, such as a sudden jump in volume on the shared IPs that doesn't originate from your sends.
Push for a clear understanding of what actions SFMC's deliverability and abuse compliance teams are taking. While they might not disclose details about other clients, they should be able to confirm they are aware of the issue and are working to mitigate it, perhaps by contacting affected mailbox providers or addressing the problematic senders. Don't be afraid to escalate the issue if initial support responses are insufficient. Sometimes, applying pressure through your sales contact can help get the problem elevated to a higher level within the organization.
Best practices for SFMC support engagement
Document everything: Keep a detailed record of communication, including dates, times, and outcomes of support interactions.
Provide data: Share concrete metrics and observations (e.g., SenderScore reports, bounce logs) to substantiate your claims.
Insist on action: Request specific steps SFMC is taking to mitigate the IP reputation damage or move your account.
Escalate when necessary: Use your sales or account manager to push the issue up the chain if frontline support is unhelpful.
One direct action you can request from SFMC is a migration to a different shared IP pool, if available and appropriate for your sending profile. Although this is not a permanent solution to the broader issue of shared IP volatility, it can offer immediate relief from a severely damaged reputation. While Salesforce's policy on shared IP use notes that lower volume senders benefit from shared IPs, it also acknowledges that shared IPs mean reputation is affected by others. For more on this, Salesforce provides official documentation.
The dedicated IP consideration
Many senders on shared IPs eventually consider migrating to a dedicated IP, especially if shared IP issues persist. A dedicated IP gives you complete control over your sending reputation, meaning only your sending practices will influence its standing with ISPs. While SFMC often advises a minimum volume (e.g., >5,000 emails/day or 100,000 messages per month) for a dedicated IP to maintain a stable reputation, a poor shared IP situation might justify an earlier transition.
The perceived "low volume" for a dedicated IP is largely historical advice related to IP scarcity and the need to generate enough data for ISPs to build a consistent profile. However, if your current shared IP reputation is consistently tanking your deliverability, even a slow warm-up on a dedicated IP can be preferable to ongoing blocklists (or blacklists). It allows you to build a clean reputation from scratch, free from the influence of other senders.
Feature
Shared IP
Dedicated IP
Reputation control
Influenced by other senders, highly volatile.
Fully controlled by your sending practices.
Volume requirement
Suitable for low to moderate volume, easier setup.
Traditionally higher volume needed for stability, but can be started with less if shared IPs are problematic.
Risk of blocklisting
Higher risk due to poor practices of other shared users.
Lower risk if your sending practices are good.
ISP perception
Can be viewed with more suspicion if the pool has many senders.
Directly tied to your brand's sending behavior.
ESP relationship
Salesforce Marketing Cloud manages shared pools and their reputation.
Salesforce Marketing Cloud provides the IP, but you manage the reputation.
It's crucial to approach a dedicated IP transition with a robust IP warming plan. This involves gradually increasing your sending volume over time to build trust with mailbox providers. Even with low initial volume, consistent sending of highly engaged mail will establish a positive sender reputation. For more details on this, learn how to maintain dedicated IP reputation with ISPs.
Building resilient deliverability
Beyond IP management, cultivating a strong domain reputation is paramount for long-term deliverability. While IP reputation is important, a robust domain reputation can often act as a buffer, helping your emails land in the inbox even if the associated IP experiences minor fluctuations. This involves consistent sending of relevant content to engaged subscribers, minimizing spam complaints, and actively managing bounces.
Proactive monitoring of your sending metrics and overall deliverability is essential. Utilize tools like Google Postmaster Tools for Gmail, and similar dashboards offered by other major ISPs, to monitor key indicators such as spam rates, IP reputation, and domain reputation. This visibility allows you to quickly identify and react to issues, rather than waiting for email performance to tank. Checking blocklists regularly is also crucial, as an IP or domain listing can severely impact deliverability.
Implementing and maintaining proper email authentication protocols (SPF, DKIM, and DMARC) also contributes significantly to your domain's trustworthiness. These protocols verify that your emails are legitimate and prevent spoofing, which in turn boosts your standing with ISPs. A properly configured DMARC record, for example, signals to receivers that you are serious about email security and authentication.
Views from the trenches
Best practices
Proactively monitor IP reputation using tools like SenderScore to detect sudden changes from shared pools.
Maintain detailed records of your email volume and engagement metrics to demonstrate your positive sending habits.
Be persistent and firm when communicating with SFMC support, escalating issues through sales contacts if necessary.
Common pitfalls
Underestimating the impact of other senders' poor practices on shared IP reputation.
Accepting vague responses from ESP support without clear action plans or timelines.
Delaying the transition to a dedicated IP even when shared IP issues become chronic.
Expert tips
Consider a dedicated IP even if your volume is 'too low' if shared IP issues severely impact deliverability.
Leverage your domain's reputation to potentially compensate for IP issues, especially with large consumer providers like Google and Yahoo.
Understand that while ESPs might not disclose details about abusive senders, they should be transparent about their mitigation efforts.
Expert view
Expert from Email Geeks says that someone abusing shared IPs is a common occurrence. It is important to push support for mitigation actions and to find out what their Abuse & Compliance team is doing.
2024-03-20 - Email Geeks
Expert view
Expert from Email Geeks says that SFMC was removed from the CSA for violations, which indicates issues with their compliance efforts. This suggests that shared IP pools may be particularly problematic.
2024-03-20 - Email Geeks
Ensuring deliverability in SFMC
Dealing with a tanking shared IP reputation in SFMC is a challenging situation, but it's not insurmountable. While you can't control other senders, you can control your response and strategy. The most effective approach involves a combination of persistent engagement with SFMC support, proactive monitoring, and a clear understanding of your IP and domain reputation.
For many organizations, the long-term solution may involve transitioning to a dedicated IP, even if current sending volumes are lower than traditionally recommended. The stability and control a dedicated IP offers often outweigh the challenges of initial warm-up, especially when contrasted with the unpredictable nature of a compromised shared pool. This strategic shift can lead to more consistent and predictable deliverability.
Ultimately, email deliverability is a continuous process of optimization and adaptation. By implementing best practices, understanding the nuances of shared versus dedicated IPs, and advocating for your sending health, you can significantly improve your chances of consistently reaching the inbox.
Gmail.
Salesforce support. Clearly articulate the issue, providing specific dates, times, and observed impacts such as increased bounce codes (e.g., Gmail 550 5.7.1 blocks) or significant delays. Reference any data you have, such as a sudden jump in volume on the shared IPs that doesn't originate from your sends.
Gmail, and similar dashboards offered by other major ISPs, to monitor key indicators such as spam rates, IP reputation, and domain reputation. This visibility allows you to quickly identify and react to issues, rather than waiting for email performance to tank. Checking blocklists regularly is also crucial, as an IP or domain listing can severely impact deliverability.
