Email deliverability in 2026 – key observations, trends & challenges for Marketers

Email marketing continues to evolve faster than ever, and deliverability has become both more complex and more critical.

At ExpertSender, we work daily with global clients and mailbox providers to monitor changes, resolve issues, and optimize performance.

Based on our close collaboration with partners across different regions, we’ve identified the key industry trends shaping 2026, along with the biggest challenges marketers will face in maintaining strong deliverability and engagement.

Observations on recent changes in the email marketing

Over the past year, the email marketing landscape has undergone a profound transformation. Mailbox providers are becoming smarter, user expectations are higher, and traditional deliverability models are losing relevance. Based on our ongoing work with global brands and ISPs, we’ve gathered key insights into how the market is evolving and what factors now have the greatest impact on inbox placement.

1. Slow adaptation to new market realities

A significant challenge remains the slow adaptation of some markets to the evolving email landscape. Many still rely on outdated assumptions, for example, believing that deliverability depends primarily on assigned IPs rather than list quality and recipient engagement. Despite our continuous education efforts, this mindset persists among part of the market.

2. Shift toward user-centric performance models

Email marketing has undergone a major transformation. Today, deliverability and sender reputation are driven almost entirely by recipient behavior, including click rates and spam complaint rates. The recipient’s reaction is now the main factor determining inbox placement.

3. Complaints as the key ISP metric

In escalation processes with ISPs, complaint rates have become the single most important indicator. Whether messages reach the inbox, land in spam, or get blocked depends primarily on how users respond. ISPs clearly communicate that user reactions are the ultimate measure of sender quality.

4. Automated filtering and monitoring periods

Anti-spam systems (e.g. Orange) now operate almost fully automatically. When complaint thresholds are exceeded, restrictions are applied, messages start going to spam or are temporarily blocked. If complaints drop over a 7–30 day observation period, restrictions are gradually lifted.

Reputation recovery is possible, but only through consistent behavioral changes and improved user engagement, not declarations or explanations.

5. Technical compliance remains essential

Deliverability standards continue to require that senders are fully authenticated and technically reliable. ISPs verify:

• SPF, DKIM, DMARC records to confirm sender authenticity,
• PTR/Reverse DNS consistency,
• Proper server configuration, TLS encryption, and legitimate message headers.

6. Quality and engagement of recipient lists as the decisive factor

ISPs increasingly evaluate:

• Complaint rates,
• Bounce levels,
• User engagement metrics,
• The ratio of active vs. inactive addresses.

Notably, domain or IP reputation, once a key signal, is becoming less important, especially with Google’s recent Postmaster Tool updates.

7. The changing perception of email marketing

ISPs are becoming more vocal about treating certain email marketing practices as potential spam. The focus needs to shift toward user experience and relevance, as ISPs increasingly prioritize the interests of their end users.

8. Recommendations for senders

To succeed under these new conditions, senders should:

• Provide exclusive, relevant content tailored to recipients’ declared and evolving interests.
• Collect and utilize deeper data beyond names and opens, such as signup sources, preferred frequency, content categories, and behavioral signals (e.g. logins, purchases).

Those who know their audiences best and act on that knowledge will continue to thrive.

Key challenges for 2026 in email marketing

Looking ahead to 2026, it’s clear that the pace of change in email deliverability will only accelerate. The introduction of stricter privacy regulations, and shifting ISP priorities will challenge even the most experienced marketers. Below are the major challenges we expect to define the year ahead, and what senders will need to focus on to stay ahead of the curve.

1. Rebuilding trust with ISPs
Mailbox providers (especially Google and Microsoft) are becoming increasingly strict toward spam-like behaviors and sending patterns that indicate poor engagement or lack of user consent.

In 2026, maintaining trust will require transparent practices, strong authentication, and consistently low complaint levels. “Quick fixes” or infrastructure changes won’t work anymore, only real behavioral improvements will.

2. Decline of IP and domain reputation as core signals
As ISPs de-emphasize IP/domain reputation (e.g., through Google Postmaster Tool changes), user engagement will become the dominant factor.

This means that list quality, interaction patterns, and complaint management will outweigh technical reputation scores.

3. Automation and AI-Driven filtering
Spam filters are becoming fully automated and adaptive, using machine learning models that analyze sender behavior in real time.

Even small deviations (sudden spikes, content patterns, engagement drops) will immediately affect inbox placement. Continuous monitoring and quick reaction cycles will be critical.

4. Affiliate model under pressure
Email marketing as we know it will face increased deliverability barriers. ISPs are tightening policies against traffic perceived as “incentivized” or “mass outreach.” The challenge will be to reinvent email communication, focusing on transparency, added value, and genuine user consent.

5. Data Privacy and Consent Management
With new regulations expected in the EU and other regions (e.g., stricter enforcement of GDPR-style frameworks), 2026 will bring greater scrutiny on data sources, proof of consent, and audience segmentation logic.

Brands will need more robust data governance and permission management systems.

6. Segmentation beyond basics
Basic segmentation based on simple demographic data or open rates will no longer be enough. True segmentation should leverage behavioral, contextual, and transactional data to deliver meaningful, timely content.

7. Reputation recovery becomes longer and harder
As AI-driven ISP systems rely on longer historical data windows, rebuilding a sender reputation after issues (spam spikes, blacklisting, high complaints) will take weeks or even months, not days.

Preventive monitoring and consistent list hygiene will be key defensive strategies.

8. Balancing volume with engagement
High-volume senders will need to balance scale with engagement quality. Sending more to unengaged users will directly harm inbox placement. Success will depend on sending less, but better-targeted emails, supported by dynamic suppression and engagement-based throttling.

9. Global fragmentation of deliverability Rules
Different regions and ISPs will continue diverging in their filtering logic (e.g., stricter policies in Europe vs. lenient ones in LATAM).

Managing multi-geo deliverability will require localized strategies and closer cooperation with regional ESPs.

10. Human oversight in a fully automated ecosystem
Even with advanced automation, success will depend on human judgment, interpreting signals, adjusting messaging strategy, and keeping the “brand voice” authentic.

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How ExpertSender helps you stay ahead

ExpertSender combines powerful technology and a hands-on partnership approach to help you master the new rules of deliverability and achieve long-term success in email marketing.

Powerful technology built for deliverability and performance

At ExpertSender, we combine advanced technology with deep deliverability expertise to help brands thrive in the rapidly changing email landscape. Our platform offers everything marketers need to maintain strong inbox placement and optimize campaign performance. With advanced analytics, clients gain full visibility into key metrics such as engagement, bounce rates, and deliverability logs, allowing them to make data-driven decisions quickly and confidently. Smart segmentation and dynamic content capabilities make it possible to personalize communication based on user behavior and engagement, ensuring that every message reaches the right audience with maximum relevance. Integrated list-cleaning tools help maintain healthy databases by automatically removing invalid or inactive contacts, protecting sender reputation and improving overall performance. ExpertSender also provides flexible warm-up options tailored to different infrastructures and business goals, as well as sophisticated automation and personalization features that make it easy to build intelligent workflows, triggered campaigns, and lead-nurturing sequences that truly engage audiences.

A partnership approach that puts Clients first

But technology is only part of what makes ExpertSender stand out. The other half is how we work with our clients. Every customer is supported by a dedicated Account Manager from the very first day, guiding them through onboarding, configuration, and optimization. We see ourselves as long-term strategic partners rather than software providers, offering ongoing advice on contact list management, segmentation, and sending strategies. Our team actively monitors performance, suggests improvements, and, when needed, engages directly with ISPs to resolve deliverability issues. Behind the scenes, we collaborate closely across our deliverability, infrastructure, and product teams, sharing knowledge and best practices to ensure each client benefits from our collective experience. This hands-on, consultative approach allows us to deliver not only reliable technology but also the human insight and strategic guidance that help our clients achieve sustainable, data-driven growth.

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Conclusion

The rules of email deliverability are changing, and 2026 will reward senders who act strategically, stay compliant, and focus relentlessly on the recipient experience.

At ExpertSender, we help brands stay ahead of every algorithm shift, deliverability challenge, and industry transformation.

👉 Book a free demo with our team to see how ExpertSender can improve your inbox placement and email marketing performance.

Authors: Agnieszka Tywoniuk, Martyna Remiszewska and Michał Kidoń