Summary
Experiencing a sudden and significant drop in email open and click-through rates, coupled with increased spam folder placement, is a common and frustrating challenge for businesses that switch Email Service Providers (ESPs). This issue often arises when migrating from a platform like HubSpot, which you've used for a decade, to a new one like Omnisend. The historical sender reputation built over years with your previous ESP does not automatically transfer to the new sending infrastructure (IPs and domains) used by Omnisend. This transition period, if not managed with a proper warm-up strategy, can severely impact your deliverability and engagement metrics.
Key findings
- ESP migration impact: Switching email marketing platforms frequently leads to changes in sending IPs and domains, directly affecting your sender reputation and email deliverability.
- Warm-up crucial: A lack of a proper IP and domain warm-up process when migrating is a primary contributor to a sudden decline in open rates and increased spam placement. Your deliverability affects all aspects of email engagement.
- Spam folder destination: Emails are landing in spam folders for previously engaged subscribers and even personal test addresses, indicating a genuine deliverability problem rather than just reporting discrepancies.
- Reputation reset: The long-standing positive sender reputation built with your old ESP (HubSpot) does not automatically transfer to the new platform's sending infrastructure.
Key considerations
- Verify warm-up process: Don't rely solely on an agency's assurance; independently confirm that a proper IP and domain warm-up was executed with your new ESP (Omnisend). This is a common cause for deliverability issues after a switch, as detailed in our guide on marketing automation platform switches.
- Check IP type: Determine if Omnisend assigned you a shared or dedicated IP address, as this significantly impacts how your sending reputation is established and managed.
- Monitor domain reputation: Utilize tools like Google Postmaster Tools to gain insights into your domain's reputation, spam rate, and other critical deliverability metrics. Our ultimate guide to Google Postmaster Tools offers further guidance.
- Authentication check: Ensure your SPF, DKIM, and DMARC records are correctly configured for Omnisend. According to Neal Schaffer's official site, deliverability impacts everything from open rates to clicks.
What email marketers say
Email marketers frequently face deliverability challenges when switching platforms. The consensus suggests that a thorough understanding of the technical migration process, particularly around IP and domain reputation, is vital. Marketers often express concern over unexpected drops in performance, highlighting the difficulty in trusting agency assurances without verifiable data. The core issue revolves around ensuring the new ESP's infrastructure is properly integrated and warmed up to maintain previous engagement levels.
Key opinions
- IP changes are standard: Many marketers acknowledge that changing ESPs almost always involves a change in sending IP addresses, which necessitates a new reputation-building phase.
- Skepticism about warm-up: There's a common sentiment that agencies might claim a proper warm-up was done, but actual results often contradict this, leading to client distrust.
- Real decrease vs. data reporting: A key concern is whether the observed decline in open rates is a true drop in inbox placement or merely a difference in how the new ESP reports metrics. For instance, email open rates have limitations that can affect accuracy.
- Loyal subscriber impact: When historically engaged subscribers report finding emails in spam, it strongly indicates a widespread deliverability issue beyond individual recipient behavior.
Key considerations
- Proactive IP check: Marketers should actively inquire about and understand their IP situation (shared versus dedicated) immediately upon switching ESPs. This is part of identifying what causes a sudden drop in open rates.
- Google Postmaster setup: Registering your domain with Google Postmaster Tools is frequently recommended to get direct insights into your deliverability performance with Gmail, a crucial first step in diagnosing issues.
- Deliverability is specialized: While marketers excel in campaign strategy, deliverability requires a different, often technical, skill set. Seeking expert advice or using specialized tools is common.
- Focus on real impact: If key audience segments (like loyal customers) are missing emails or finding them in spam, it confirms a real problem that needs urgent attention to fix low email click-through rate.
Marketer view
Marketer from Email Geeks indicates that changing domains or IPs without a proper cut-over and warm-up process can significantly contribute to deliverability issues after an ESP switch.
Marketer view
Marketer from Email Geeks states that IP changes are a normal occurrence when migrating from one email service provider to another.
What the experts say
When deliverability tanks after an ESP migration, experts emphasize a systematic diagnostic approach. The primary concern is whether the observed drop is a genuine filtering issue or merely a reporting discrepancy. If it's real, the focus shifts to identifying which mailbox providers are directing emails to spam and scrutinizing technical configurations like email authentication and link tracking. The transition to a new ESP essentially resets your sender reputation, requiring a careful rebuilding process.
Key opinions
- Data accuracy first: Experts stress the importance of determining if the decrease in open rates is a true decline in inbox placement or if the new ESP's reporting differs from the old one.
- Spam folder culprit: If the decrease is real, the most probable cause is emails being sent directly to the spam or junk folder, bypassing the primary inbox. Our guide on why your emails are going to spam provides a detailed explanation.
- ISP-specific issues: Identifying specific Internet Service Providers (ISPs) or mailbox providers that are heavily filtering your emails is crucial for targeted troubleshooting.
- Authentication is key: Comprehensive email authentication setup (SPF, DKIM, DMARC) is foundational for good deliverability. Learn more with our simple guide to DMARC, SPF, and DKIM.
- Link domain concerns: If tracking links in your emails do not align with your sending domain, it can raise red flags with spam filters.
Key considerations
- Use diagnostic tools: Leverage specialized tools to check your email authentication configuration and identify potential issues that could be impacting deliverability. For example, subject lines alone determine opens and spam reports.
- Postmaster tools access: Ensure your domain is registered and verified with Google Postmaster Tools for invaluable data on your Gmail performance, spam rates, and domain reputation. This helps understand why emails go to spam.
- Domain reputation rebuild: Understand that switching ESPs means starting over with a new domain reputation on the new platform's IPs, even if your domain previously had a strong reputation. Consistent sending and good engagement are critical to rebuild it.
- Holistic view: Consider all factors influencing deliverability, including content quality, recipient engagement, list hygiene, and technical setup, as they collectively impact inbox placement.
Expert view
Expert from Email Geeks suggests that the first step in diagnosis is to determine if the observed open rate decrease is a genuine deliverability issue or simply a variation in how the two ESPs (HubSpot and Omnisend) report data.
Expert view
Expert from Email Geeks states that if a real decrease in open rates is confirmed, it is likely due to emails consistently landing in the spam folder rather than the intended inbox.
What the documentation says
Official documentation from major mailbox providers (like Google and Microsoft) and industry standards bodies consistently underscores the importance of proper email authentication, disciplined sender reputation management, and adherence to established best practices. These guidelines are particularly critical during a significant infrastructure change, such as migrating to a new ESP. Failing to align with these documented standards can lead to severe deliverability penalties, including emails being routed directly to the spam or junk folder.
Key findings
- Authentication is mandatory: Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC) are fundamental requirements for establishing sender trust.
- Reputation is dynamic: Your sender reputation is continuously evaluated based on sending behavior, recipient engagement, and spam complaint rates. It is intrinsically linked to the sending IP and domain used.
- Warm-up guidance: Documentation provides specific guidelines for warming up new IPs or domains, gradually increasing volume to build a positive sending history with mailbox providers.
- Engagement signals: Positive engagement metrics (like opens and clicks) and low spam complaints are crucial signals that mailbox providers use to determine if an email is legitimate and desired by recipients.
Key considerations
- DNS record accuracy: Double-check all DNS records related to SPF, DKIM, and DMARC to ensure they are correctly configured and pointing to your new ESP, Omnisend, to prevent authentication failures.
- IP type implications: Understand the differences and implications of sending from a shared versus a dedicated IP address with your new ESP, as this impacts reputation management.
- Postmaster tool integration: Integrate with and regularly monitor Google Postmaster Tools for crucial feedback on your sending performance, including spam rate and domain reputation, which is essential to improve your domain reputation and avoid Gmail's spam filters.
- Content and list quality: Even with correct technical setup, poor content or an unengaged list can lead to deliverability issues. Optimizing content and segmenting your list can help to increase your open rates and reduce spam complaints.
Technical article
Google Postmaster Tools documentation states that your sender reputation is the primary factor determining whether your emails are delivered to the inbox, filtered to spam, or rejected entirely.
Technical article
Microsoft documentation outlines new sender requirements for Outlook and Microsoft 365, emphasizing strict adherence to authentication standards (SPF, DKIM, DMARC) and maintaining low spam complaint rates.
Related resources
9 resources
Related pages
Why do marketing automation platform switches cause drop in email open rates?
What causes a sudden drop in email open rates?
Why has my email open rate dropped suddenly and what can I do?
Why did my email have lower open rates in Gmail, and go to spam?
Why Your Emails Are Going to Spam in 2024 and How to Fix It
Ultimate Guide to Google Postmaster Tools V2
How to Run an Email Deliverability Test: A Proven Checklist
A simple guide to DMARC, SPF, and DKIM
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How to Improve Domain Reputation Using Google Postmaster Tools [2025 Guide]
