How to make the disk space free to 0mb when all the data has been erased

I have faced an issue in mail quota. The mails seems to be bounced because of this issue.

I have created a mail-id as sanju@test.com for the domain test.com with quota as 7MB. Now even after clearing all the data from Inbox,Trash,Sent it shows the disk space usage as 5.6mb for sanju@test.com.

How to make the disk space free to 0mb when all the data has been erased?

1. I have cleared the spam folder for sanju@test.com and the email account is showing correct disk space usage.

You should login to the server via SSH to clear the spam folder.

>> Login to the VPS

>> Go to /home/[username of the domain]/mail/[after @]/[password of the mail-id]/.spam/new and clear the emails.

or

2. To delete the spam mails without receiving the mails into the above folder.

>> Login to cpanel.

>> Go to Mail -> SpamAssassin.

>> Click on "To simply have the server DELETE and NOT deliver emails that are tagged as spam by SpamAssassin, click here now".