How to clean up my Mailbox?
To clean your Mailbox, go to your Site Tools > Email > Accounts. Choose the email account and go to the Actions menu > Log in to Webmail.
Delete the messages that you do not need and empty your Junk/Trash folders to save space. If you are using an email client such as Thunderbird, Outlook, or MacMail you can do the same via your email client.