If your IP address is on the black list, then the mailing will not be sent or will have to go through additional spam filters. According to Forrester Research, spam messages make up 67% of all email traffic. That is why ISPs should protect their clients from these types of messages. This can be achieved by filtering messages and checking the legality of the mail delivery. Using black lists, the ISPs can reduce the amount of spam messages in their networks.
Email providers use black lists that are compiled on the basis of publicly available information and internal ISP data. The black lists use different spam identification algorithms, for example "unwanted email." If you send "unwanted email" and it collects a lot of spam complaints, then there is a high probability that you will get onto the black list.
If your mailing has a high percentage of subscribers who mark your letter as spam, then the SendPulse server will get onto the black list. That is why when using our server, you should follow the rules of our Antispam Policy.