Spam test tools are a great way to quickly gauge the sender’s inbox placement; however, you should ultimately focus more on your Klaviyo data instead of over-relying on seed list test results. If your results indicated that there is a widespread spam issue for your account, you would see this reflected in open rates. We always recommend comparing the seed list test results with their Klaviyo data. For example, if the seedlist test reports that a high percentage of emails sent to Gmail were placed in spam folders, then we would expect the open rates to reflect that (i.e., lower open rates). Advanced reports of campaigns and flows are the best place to look within Klaviyo. 

For more information on  How to Monitor Deliverability Performance, check out this article.