Email Restore Without Delete current Email

hello

i have problem.
let say domain.com have user1@domain.com 100 email
i create full backup and email folder backup at jan 1st 2022. then i clean the user1@domain.com

now the user1@domain.com already have 25 new email
the question is
how to put the old 100 email to user1@domain.com without losing current email ?