IP addresses or email domains associated with spam.

Once an email domain is blacklisted it will have reduced delivery rates.

By using a reputable email service provider (such as EcoSend) email marketers can avoid being blacklisted. In addition, it's essential to follow good email practices so that emails are not flagged as spam by email servers or recipients, which could also lead to blacklisting.

It is thought that 85% of all emails sent are spam, and blacklisting is one of the ways that email providers look to eliminate the problem to provide a better user experience.

If an email address or domain is blacklisted, it can be challenging to recover from. Therefore, email marketers should be very aware of how to remain both trusted and compliant.