Changing email account doesn't release that email

[isyq]

I set the admin account to xxx@mail.com, after built everything up, I change it to yyy@mail.com.
Now I try to set a new user with that email(xxx@mail.com), it always alerts the email is already existed.

[lunny]

What's the version of you Gitea instance?

[isyq]

"gitea.exe --version" shows: Gitea version 1.15.6 built with GNU Make 4.1, go1.16.9 : bindata, sqlite, sqlite_unlock_notify.

[lunny]

How did you change the old user's email to yyy@mail.com?

[isyq]

Login admin's home page -> 'Site administration' page -> User accounts -> Change itself email address.