When it comes to deliverability, the biggest mistake people make is dealing with bounces incorrectly—sending emails to addresses that don’t exist.
It’s more common than you’d think. Whenever I start with a new client, especially if they haven’t sent emails in a while, the first step is to create a segment of people who have bounced. If they’ve been sending emails, I focus on those who bounced in the last 30 days. If they haven’t sent emails in, say, the last 180 days, I look for anyone who has bounced even once over all time.

This becomes our “no-go” segment. We don’t want to email these people.

Why?

Because their emails bounced. A bounce essentially means their email address isn’t reachable. This could happen for several reasons—maybe their inbox is full, or maybe the address never existed. Honestly, it doesn’t matter why.

What does matter is keeping bounces to a minimum, especially if you’re restarting email campaigns after a break. In a platform like Klaviyo, profiles that bounce too many times will eventually be suppressed automatically. However, being proactive is key because high bounce rates can seriously harm your sender reputation and lead to more emails landing in spam.

Here’s what I do (and what you should do):

1. Create a bounce segment.

In Klaviyo, define this segment as anyone who has bounced at least once in the last 30 days. If you’re restarting after a long pause, include anyone who has ever bounced.

2. Exclude this segment from your campaigns and flows.

This ensures you’re not repeatedly emailing invalid addressess

3. Don’t suppress them right away.

Instead, spread out the bounces across multiple emails. For example, sending 10 emails that each bounce to 5 addresses is far better for your deliverability than sending one email with 50 bounces. Over time, Klaviyo will suppress those profiles automatically.

If those emails stop bouncing, great! You’ve avoided suppressing a potentially active subscriber. But if they don’t? No problem—Klaviyo has your back. Either way, you’re protecting your deliverability and keeping your email list clean.