You can only unblock email addresses on Yahoo Mail using the desktop website — the mobile app doesn't give you the option.

Overview Blocking emails helps reduce spam and unwanted messages instantly.Unblocking allows missed contacts to be smoothly reintroduced into your inbox.Gmail, ...

Unblocking someone on Gmail is simple. On a PC, go to Gmail’s Filter and Blocked Addresses settings to see a list of blocked emails, where you can unblock one or more addresses. In the Gmail app, ...