Internet Protocol, better known as IP address is a unique set of numbers assigned to each internet-enabled device. An IP address allows devices to send and receive data to and from specific devices in a given network.
Nowadays, we have two standards of IP addresses – Internet Protocol Version 4 (IPv4) and Internet Protocol Version 6 (IPv6).
IPs get blacklisted if someone has reported them. It is possible that from the IP got blacklisted for sending out spam emails.
It is possible that someone might be sending out tons of emails using your IP address. Ensure that your security features are updated and reliable.