If your email address has changed support can change your email address upon request however this is different than providing a new user access.
In order to change the access to the system and owner of projects you must reach out to your Licensor contact for each account the email is registered to. The Licensor will need to invite the new email and they will be able to assign the same access. If there are projects associated with the old account the Licensor Site Administrator can transfer those or if the user needs access in addition to you projects can be added to new user in addition to you.
Note: Mediabox is not permitted to add new users to our partners sites, or assign access to projects for a new user.