There are several reasons why email addresses can get blocked:
Spam Complaints: If recipients mark your emails as spam, their email addresses might get blocked by your ESP. Hard Bounces: When an email fails to deliver due to a permanent reason, such as an invalid email address, it is termed a hard bounce. Multiple hard bounces can lead to blocking. Soft Bounces: These are temporary issues like a full inbox. Repeated soft bounces can also lead to addresses being blocked. Inactive Subscribers: If users donât interact with your emails over a long period, the ESP might block these addresses to maintain deliverability rates.