Being over quota means you have exceeded your mailbox's size limits. All of the information in your mailbox is stored on a server, and each mailbox has a specified amount of space on the server. Once you've filled up the available space, you will not be able to receive any more email, or add any further information to your mailbox until you have the space to do so.
There are a few options available for creating extra space in your mailbox which are outlined below.
Empty your Trash
Deleting your email from your inbox doesn't mean its gone for ever; it just means that its been moved to the trash folder. You can empty your trash folder to remove the email from your server completely, creating more space for you to receive emails.
To avoid having to manually remove the trash you can set your webmail client to automatically permanently delete anything you send to the trash folder. Simply access the options menu, and then select the preferences section of the email options; then select Yes for the Permanently remove deleted emails? Setting.
Back up your Email
One way of making space in your mailbox is to create a backup of your old emails, allowing you to move them to a local drive and delete them from the server, without losing them. This allows you to save your email directly from your webmail client to your hard drive. Use Archive in your mail client (i.e. Outlook) to do this and remove the tick “leave a copy of the messages on the server”.
Clear your sent messages
As with your deleted messages, your sent messages can hang around on the mail server, hanging on to valuable space that you could be using for more important matters. As before, when you delete from your Sent message folder, make sure you also empty your trash!
Simply access your sent items folder by clicking on the Sent folder from the left hand column, and then use the delete button from the tool bar at the top of the page.
