Blacklist is managed in menu > Settings > Mail > Blacklist and whitelist. The ‘Manage Blacklist’ button will open a window where you can add or remove any email addresses or domains.

Local blacklist is available to everyone. From eM Client 10.1, we also offer support for server-side Blacklist as well as Whitelist for IceWarp and SmarterMail accounts.

You can read about the Blacklist and Whitelist feature in more detail in our blog post here: eM Client Blacklist & Whitelist

eM Client 9 and older:

You can view and manage the Blacklist rule in menu > Rules on Windows or in Tools > Rules on macOS. Just select the Blacklist and click the 'Edit' button.

A new window with all the domains and addresses in your blacklist will pop up and you can add new items or remove any of the email addresses and domains already in it.