To enable the email backup option in the Exchange Admin Center (EAC) through the import/export feature, follow these steps:
Assign the Mailbox Import Export Role:
By default, the Mailbox Import Export role isn’t assigned to any role group. You need to add this role to a role group that you belong to, such as the Organization Management role group.
In the EAC, go to Permissions > Admin roles.
Select the role group you want to add the role to (e.g., Organization Management), and then click Edit.
Under Roles, click Add and select Mailbox Import Export. Save the changes.