Key Takeaways
- B2B email deliverability is becoming harder as inbox providers raise the bar: Corporate filtering, stricter DMARC authentication requirements, one-click unsubscribe rules and complaint-rate standards are making inbox placement more dependent on trust, compliance and sender reputation.
- AI and engagement signals are reshaping email visibility: Mailbox providers are using AI-powered tools and behavioral data to prioritize relevant messages, while emerging KPIs such as Disaffection Index, Reply Rate and Quantified Trust may help marketers measure success in 2026.
Email deliverability is getting harder to manage at the very moment it matters most. For B2B marketers, reaching the inbox now means navigating a more complex path shaped by layered corporate filtering, stricter authentication standards and evolving mailbox provider expectations.
Validity’s latest Email Benchmark Report underscores just how quickly the landscape is changing, as senders face growing pressure to prove trustworthiness, maintain compliance and earn visibility with increasingly selective inbox algorithms.
The report digs into a broader shift in how mailbox providers evaluate email performance— requirements around Domain-based Message Authentication, Reporting, and Conformance (DMARC), one-click unsubscribe and complaint rates are raising the baseline for sender quality, while engagement signals are playing a larger role in determining which messages get seen. At the same time, AI is reshaping both sides of the inbox experience, helping marketers sharpen targeting while enabling mailbox providers to prioritize, summarize and rank messages based on user behavior and relevance.
In this Q&A, Guy Hanson, VP of Customer Engagement, Validity, shares his perspective on the trends shaping email performance. The conversation explores B2B inbox placement challenges, the impact of AI on email visibility and deliverability, and the emerging email KPIs that could help define success in 2026.
Demand Gen Report (DGR): Guy, thanks for taking time out our schedule to discuss the findings in Validity’s report. What are the key factors that make it more difficult for B2B emails to reach the inbox?
Guy Hanson: Thanks for having me. B2B senders face what I’ve started calling a double whammy. Most business recipients sit behind two layers of filtering controlled by only a few companies. Office 365 and Google Apps dominate the hosting layer, and Proofpoint controls more than half of the corporate filtering layer. Messages have to satisfy both to reach a human being, and their standards aren’t fully transparent, fixed or aligned with each other.
Authentication is the other big factor. Because a business email typically passes through multiple security layers before reaching its recipients, there are more opportunities for SPF or DKIM checks to fail. ARC can help preserve the original authentication results, but only when the intermediate platforms support it. B2B senders need to understand how their messages are routed to the inbox so they can catch possible failure points beforehand.
DGR: What was the average global inbox placement rate in 2025, and what drove the improvement?
Hanson: The average global inbox placement rate for 2025 was 87.2%, a 3.7% increase since 2024. A big reason why is that Gmail, Yahoo and Microsoft now all enforce mandatory guidelines around DMARC authentication, one-click unsubscribe and low complaint rates. That enforcement has lifted the quality bar across the board. New laws like the EU Artificial Intelligence Act, plus nearly half of US states now having new-generation privacy rules in place, have also pushed senders toward better practices.
The uplift was largely concentrated on the consumer side. Europe hit 91.1%, Germany landed at 97.5%, and South America posted the biggest year-over-year jump at 10.6%. B2B senders moved in the opposite direction, with inbox placement falling 1.3% at hosting platforms and 5.8% at corporate filters. The takeaway is that programs need to pay attention to where their actual audiences read email, not where the aggregate numbers look healthiest.
DGR: How are mailbox providers prioritizing user engagement, and what risks do B2B brands face if they don’t adapt?
Hanson: Most major mailbox providers added features in 2025 that prioritize emails based on user behavior. Gmail launched Manage Subscriptions and a “Most Relevant” view of the Promotions tab. Yahoo rolled out Catch Up and added an Insights tab to Sender Hub. Apple extended its redesigned Mail app with Apple Intelligence to push time-sensitive messages to the top.
These features tend to reward senders who get consistent, steady engagement with more visibility in the inbox than their competition. That’s challenging for many B2B brands because engagement is so often tied to business needs that aren’t always predictable. Real estate is the cautionary example in our data, with Gmail spam rates at 20.7%. The tough economic climate is making it harder to generate consistent engagement, and it was already challenging with the pronounced time between transactions.
DGR: Which mailbox provider was the toughest to send to in 2025, and how did new bulk sender requirements impact deliverability?
Hanson: Microsoft remained the toughest at 77.4% inbox placement, more than 12 percentage points below Gmail’s 89.8%. Deliverability did improve in Q2, when Microsoft introduced similar rules to Gmail and Yahoo, rewarding the many senders already compliant with those rules. The big four mailbox providers are converging on a shared set of expectations, and that convergence has been good for subscriber trust because authentication and easy opt-outs are now table stakes.
For B2B marketers trying to crack Microsoft specifically, watch your Sender Reputation Data rate closely. That’s Microsoft’s direct read on how subscribers feel about you. Tighten authentication to at least p=quarantine on DMARC, ideally p=reject.
DGR: What are the key differences between email delivery and deliverability, and why do they matter for B2B campaigns?
Hanson: Delivery and deliverability are often used interchangeably, and that’s a problem. Delivery is a simple “sent minus bounced” calculation. It only confirms that the receiving mail server accepted the message, which tells you nothing about where the message actually landed. Deliverability is the sender’s ability to reach the inbox specifically, and not the spam folder, the gateway quarantine or a custom quarantine a corporate admin created for manual review.
For B2B campaigns, the stakes are especially high because the delivery metric can look great— even 98% or 99%— while actual inbox placement is far lower. A sales team pulling a lead list and seeing a near-perfect delivery rate has no idea that half their outreach might be sitting in a corporate quarantine.
DGR: How is AI influencing email marketing, and what specific areas are shaping deliverability for B2B campaigns?
Hanson: Three areas matter most. On the sending side, behavioral segmentation and subject line testing are getting sharper, which produces smaller, more relevant sends that generate better engagement. On the receiving side, every major MBP is building features that grow the gap between senders who produce interaction and senders who don’t.
Cybercriminals are using AI, too. There’s a platform called SpamGPT that gives scammers a CRM toolkit for sophisticated phishing. The more convincing fraudulent messages get, the more pressure mailbox providers will put on authentication— so B2B senders need to make sure their authentication is up to par.
DGR: How is Gmail integrating AI to transform the inbox experience, and how might this affect B2B sender visibility?
Hanson: Gemini turns the inbox into an assistant. Users can ask questions about their email, and the tool surfaces messages based on previous response patterns and engagement history. In essence, relationship depth is beginning to decide inbox ranking instead of recency.
The practical response, beyond prioritizing relationship-building, is to start treating emails the same way SEO professionals treat search. Write for a machine to easily understand and restate your message. Front-load key information, use clear headlines, add meaningful alt text and format for machine readability. That way, when Gemini summarizes your email, it captures what you actually want the reader to know.
DGR: What is the significance of the year-over-year reduction in global sending volumes in 2025 for B2B marketers?
Hanson: The bigger point is that volume is no longer a reliable growth lever. Marketers have long known that targeted sends outperform broadcasts on a per-email basis, but the targeting tools weren’t precise enough to replace the reach that such volume provided, and mailbox providers tolerated high-volume sending in ways they no longer do.
The combination of new bulk sender requirements and AI-powered targeting has finally made “less and better” a viable commercial strategy, not just a theoretical best practice. Triggered sends create 10 to 15 times more revenue per email than broadcasts, and last year, 2% of total email volume accounted for 37% of email-driven sales.
That applies beyond polished campaigns, too. Many businesses also count sales cadences and one-to-one prospecting as part of their B2B email engine. Those messages can harm engagement as well when they’re poorly timed or targeted.
DGR: How did deliverability for B2B senders change in 2025, particularly for hosting platforms and filtering companies?
Hanson: Hosting platforms saw a modest 1.3% decline, and filtering companies dropped 5.8%. B2B marketers should pay closer attention to that 5.8% figure. A big part of what’s driving the decline is the authentication issue I mentioned earlier. Emails forwarded through corporate filters can fail SPF validation when the forwarding IP doesn’t match the original sending IP, and filters increasingly treat authentication failure as a signal to quarantine.
The other factor is that filtering companies are responding to the same engagement signals mailbox providers are, just with less visibility into end-user behavior. Fixing this requires rethinking what a B2B email program is trying to earn, which now comes down to sustained relevance for a defined audience.
DGR: What are the three emerging email KPIs that Validity predicts will go mainstream in 2026, and how can they help B2B marketers gauge success?
Hanson: The three are Disaffection Index, Reply Rate and Quantified Trust.
The Disaffection Index combines unsubscribes, complaints and bounces into a single ratio against clicks: (Unsubscribes + Complaints + Bounces) / Clicks × 100. With a 0.3% unsubscribe rate, 0.1% complaint rate and 0.1% bounce rate against a 1% click rate, the Disaffection Rate is 50%. For every two clicks, one subscriber is lost. When that number exceeds the click rate, the program is shrinking its own audience every time it sends.
Reply Rate is Replies / Delivered Emails × 100. Microsoft has made clear that replies are one of the strongest engagement signals they track, which means the no-reply address needs to retire. Reply rate is also particularly useful because you can design for it. Emails that invite a specific response or ask a question outperform broadcast-style sends.
Trust borrows from the iconic model for trustworthiness in David Maister, Charles Green and Robert Galford’s book, “The Trusted Advisor”: Trustworthiness = (Credibility + Reliability + Intimacy) / Self-Orientation. Most B2B programs score badly on self-orientation because they’re built around the sender’s calendar, product launches and pipeline goals. Winning programs in 2026 will rebuild around the recipient instead.
