The Reply Rate Breakdown

Hey there,

Kevin from Astris Partners with another edition.

A founder asked me last week why his reply rate dropped from 3% to 0.4% in six months. Same messaging, same targeting, same everything.

Except it wasn't the same. Three things changed in his infrastructure without him noticing, and each one killed a piece of his performance.

This is what most people miss. Reply rates aren't just about copy. They're about a system. And in 2026, that system has more failure points than ever.

the reply rate equation

Most founders think it's simple: good copy plus good targeting equals good replies.

The real equation looks like this:

Emails sent → Authentication pass rate → Inbox placement rate → AI filter pass rate → Open rate → Reply rate

Each step is a multiplier. If you're at 60% authentication pass rate, 40% inbox placement, and 30% AI filter pass rate, you're already down to 7.2% of emails even reaching a position where they can be opened.

Then you need compelling copy to get the open and reply.

where the leaks happen

When we audit failing campaigns, here's what we find:

40% have authentication issues. SPF or DKIM misconfigured, DMARC not set up, domains not properly warmed. Emails bounce or go to spam before anyone sees them.

35% have sender reputation problems. Sending from a primary domain, previous spam complaints, sudden volume spikes. Gmail and Outlook have already flagged the domain.

15% have list quality issues. Bad data, saturated contacts, no engagement signals. Even perfect emails can't save a bad list.

10% actually have messaging problems. The copy is generic, the value prop is unclear, the call to action is weak.

Most founders obsess over the 10% while ignoring the 90%.

what changed in 2026

Google's AI Inbox made the equation harder. Now there's an additional filter between delivery and visibility. Your email can pass authentication, land in the inbox, and still get buried in a low-priority view that no one checks.

The AI learns from engagement patterns. If your sending domain has low open rates and minimal replies, future emails get filtered more aggressively. It's a compounding problem.

This is why companies that let their infrastructure degrade can't just "fix the messaging" and recover. The system remembers. Rebuilding sender reputation takes weeks of careful volume management and engagement rebuilding.

the companies winning

The ones hitting 5-8% reply rates in 2026 all have the same thing in common: they fixed the infrastructure first, then optimized the messaging.

They're sending from multiple clean domains with proper authentication. They're using signal-based lists with high engagement potential. They're managing volume and warmup strategically. And only then are they testing messaging variations.

The copy still matters. But it can't overcome broken infrastructure.

Talk soon,

KP

P.S. If you're stuck with low reply rates and you're not sure where the breakdown is happening, I can show you. We'll audit your setup and pinpoint exactly where you're losing performance. Book a strategy call here.