The news: Email deliverability issues are costing businesses revenues and engagement. Spam filters, bounce rates, and data quality issues are the largest culprits.

• Issues reaching inboxes have directly affected revenue or customer retention for 64.6% of US businesses, per Kickbox’s 2025 Email Deliverability Survey.
• Spam filtering is the biggest barrier to reaching consumers for 60.3% of businesses, followed by low engagement (16.4%) and poor email data quality (9%).

Why does it matter? Deliverability issues can be costly and dampen contact with potential customers.

• Companies invest 26.6% of their marketing spend on email on average.
• The average email open rate across all industries is only 21.5%.

Email marketing is also a favorite among consumers—when it can reach them. 69% of US consumers said emails is their preferred communication channel with brands, per Emarsys, compared with 53% for SMS/MMS and 48% for direct mail.

Damaged trust: High bounce rates and spam complaints can cause internet service providers (ISPs) to start filtering out emails from senders, compounding any other delivery problems.

• Having a bad sender reputation is the biggest barrier in reaching inboxes for 5% of businesses, per Kickbox.
• Use of AI in email marketing—a growing tactic—can also activate spam filters and reduce deliverability.

Confirmation is necessary: Verifying email lists before sending campaigns can help inbox placement and engagement, but not all businesses do so.

• Less than a quarter (23.6%) of email marketers verify their email lists before each campaign.
• It’s also crucial to monitor revenue loss due to poor deliverability, which nearly two-thirds (61.6%) of businesses haven’t done.

Our take: Avoiding ISP blacklisting should be a top priority for email marketers, as even a few missteps can hurt deliverability.

Customizing content for specific customer lists, removing inactive email subscribers, verifying emails at the time of sign up, and asking for confirmation before subscribing can all help email marketing campaigns perform better.