special.usps.com being blocked by NextDNS

I cannot answer the why, but adding usps.com to allow list fixes the problem. Perhaps the destination host at cloudfront.net also hosts unrelated services that google safe browsing considers to be unsafe.

Google Safe Browsing

Block malware and phishing domains using Google Safe Browsing — a technology that examines billions of URLs per day looking for unsafe websites. Unlike the version embedded in some browsers, this does not associate your public IP address to threats and does not allow bypassing the block.