Hi @Hylink Digital, 

Welcome to the Community! Happy to help! 

To be clear, do you mean that you sent our 4 live test campaigns before sending out the campaign to a larger group of people or you sent 4 previews of your campaign? If these were live campaigns sent to individuals, you can go to their Klaviyo profile and see whether not the have the ‘received email’ metric recorded to their profile. Additionally, did you send the live tests or previews to the same person four times or once to 4 different people?

Did all the recipients who did not find the email check their ‘Spam’ and ‘Promotions’ tab of their inboxes for the email? Our Help Center has some insightful documentation on Why Some Preview Emails Go to Spam. Additionally, Klaviyo is only the sending service, not the delivery agent of emails. An inbox provider is the one that decides whether or not an email is received and if so, where it lands in the inbox. If these emails were sent to different inbox providers, the reason some inboxes didn’t receive the email could be because emails are being blocked due to an inbox provider's DMARC settings. 

Finally, I’d suggest checking out this similar post relating to why another’s preview sends were not received at all to gain additional insight into how inbox providers work. 

Thanks for sharing your question with us! 

-Taylor