You can upgrade your email-box when your current one is running out of space or you need to change from the trial to a paid service.
For upgrading your email-box you need to have an additional package with at least one email-box available on which to move your email-box.
It is important to underline that the size of the new email-box must be the same or bigger of the current email-box.
It is not allowed to upgrade to an email-box with a smaller size.
For upgrading your email-box your need to click on:
Mailboxes management -> Mailbox_list -> Change_package