Hello @ehargeryoung,

Welcome to the Klaviyo Community!

Email bouncing can occur for a wide variety of reasons as explained in our About Bounced Emails in Klaviyo Help Center article. Bounces often times occur as something on the recipient’s end. In my experience, if you’re seeing a large number of emails bouncing for recipients with the same domain that were previously able to receive the email; this is often times caused by the email being undeliverable due to an error with the recipient server or the email was blocked by the recipient server.

When an email is undeliverable due to an error stemming from the server, they are typically resolved fairly quickly. You’ll want to reach out to the inbox providers or review those inbox provider’s status reports to see if there were any public reason for the emails being undeliverable. 

On the other hand, emails that are blocked by the recipient’s server would be indicative of a decrease in your sending reputation due to negative sending behaviors. When this happens, there will usually be indicators leading up to this point as detailed in the How to Troubleshoot Decreasing KPIs Help center article. When this occurs you’ll want to go through a warming process and strengthen your sending reputation again. 

You may also find it helpful to take a look at some similar Community post pertaining to this subject. I’ve linked some below to get you started:

I hope this helps!

David