Northern Trail Outfitters (NTO) has noticed a decrease in open rate across all email campaigns.

Block bounces are a critical metric to analyze when assessing sender reputation. High block bounce rates indicate that emails are being rejected by ISPs due to issues such as poor list quality, spam complaints, or reputation problems. This metric can provide insight into the health of your sender reputation and whether the recent importof subscribers may have negatively impacted it. This approach is verified in Salesforce Marketing Cloud documentation on monitoring and maintaining sender reputation.