Why are some QUIC.cloud IPs blacklisted?

From time to time, QUIC.cloud IP addresses are blacklisted on reputation services like MxToolbox. This happens because reputation services will usually blacklist the entire subnetwork when an IP becomes problematic.

So, if a service or provider gets blacklisted for sending spam email, for example, and that server’s IP is in the same subnetwork as a QUIC.cloud IP,  the QUIC.cloud IP is also blacklisted automatically. This is why it is usually not possible to simply remove a single IP address from these blacklists.

This is nothing to worry about, as it does not affect your email service.