From Forminator email settings, the 'Send admin(s) email' options search result can a bit confusing.
When you start typing a username in the field, the suggestions that popup are the user emails instead of the actual username.
For example, a username 'manager', when typing 'man' it suggests user email but nothing in the email address matches the string 'man'.
If more than one email address returned from the query, it makes it difficult to guess which email is for the user. Unless the email for the specific username is known.