How do I unblock a domain I just blocked @gmail.com

How do I unblock a domain as I just blocked @gmail.com

Hi Jason, what do you mean by blocked @gmail.com? Did you blacklist the domain?
If you blacklist a domain or an email address to edit the blacklist, please go to Tools > Rules > Blacklist, and edit the list of blacklisted domains/emails.

Hope this helps,
Paul.