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Around the start of the new year, Kaczyński convened a meeting with his colleagues. They knew how they’d fallen out of client inboxes, but not how to get back in. With another holiday season over the horizon, Kaczyński’s team agreed it was time to ask a third-party deliverability agency for help. The agency performed an audit, then recommended some tough but necessary changes.

Bouncer would need to turn loose subscribers who had stopped engaging. They would create separate subdomains for marketing, transactional and corporate emails so that spam issues in one communication channel couldn’t cascade to others. And instead of blasting out mass emails, they would drip-feed non-time-sensitive sends across multiple days.

Within two or three weeks, the company was able to start communicating with its audience again, and after a few months, it was back to sending at its usual volume. The real test would come in the leadup to Black Friday 2025, when it finally had a chance to recover the sales it had missed out on the previous year.

While some companies revamp their sending strategy to chase better deliverability, others choose the path of least resistance. OutVoice, for example, simply weathered the storm and waited for anti-spam algorithms to move on to another unsuspecting victim. 

After a few months, Study Hall miraculously began appearing in subscribers’ inboxes again—without the phishing warnings that had haunted its previous sends. Diao was relieved that subscribers had stuck around through the rough patch, but he never got the closure he had hoped for. “I’m hoping it doesn’t happen again,” he said. “I don’t know that we’re any more prepared for it than we were before.”

Diao understands that mailbox providers err on the side of caution because they want to protect their users from harm. But he thinks there should be more mechanisms for well-intentioned companies to talk to those services during deliverability emergencies. Ideally, he said, senders would have more avenues—a helpline, for example—to make their case and compel mailbox providers to listen. “If they had the power to just destroy businesses like that, there should really be an appeals process that happens quickly,” he said. 

Still, separating well-meaning senders from bad actors is complicated, Iverson said. Independent anti-spam blocklists and email giants alike are struggling to keep up with spammers, who increasingly use AI and other emerging technologies to evade algorithms. While anti-spam filters sometimes overcorrect and block well-intentioned senders, the alternative might be a return to the early 2000s, when inboxes were flooded with junk. “It does take a lot of work to keep email usable as a good communication ecosystem,” he said. “Even though you can’t see the underside of the duck, there is furious paddling happening to keep this ecosystem working.”

Besides, anti-spam filters might be the wakeup call some organizations need to rethink their sending strategy. “Sometimes I find that they’ve actually done you a service by ringing the alarm,” said Bonar, the deliverability summit cofounder. “Each of those spam complaints or unsubscribes, because you’re doing something wrong, is actually cutting into your bottom line.”

In the crucial weeks ahead of this year’s holiday season, Kaczyński’s spam folder remained refreshingly empty. After cutting its subscriber list by almost half and promoting a sale nearly identical to last year’s—and with the holiday season only half over—the startup had already registered 35% year-over-year growth, compared to 5% the year before. All told, it took nearly a year of scrappy experimentation to get back on track.

“In 2024, we just missed the wave,” Kaczyński said. It’s a completely different picture this time. “All the knowledge, experience, safeguards and routines that we have right now, plus really good, stable base deliverability, will let us ride the wave during the busiest time of the year.”