In version 9, go to Menu > Settings > Mail > Privacy > Blacklist > Manage Blacklist.
In version 10, go to Menu > Settings > Mail > Blacklist > Manage Blacklist.
Select the email address or domain, and click on Delete
In version 9, go to Menu > Settings > Mail > Privacy > Blacklist > Manage Blacklist.
In version 10, go to Menu > Settings > Mail > Blacklist > Manage Blacklist.
Select the email address or domain, and click on Delete