If you have a mailbox that is always going over-quota or filling up with mail like your default account or your spam box and you don't want to have to keep logging in and deleting the emails manually this howto will show you how you can have it automatically deleted.

Login to your cpanel and click on the Cron jobs icon
Next click on the Advanced (Unix Style) button to open the cron manager.
Now let's say you want to have *ALL* the emails in your default email accounts inbox deleted that are older than 10 days and have it run at 6:45 AM each day.

To do this enter the following information in the following fields:
Minute: 45
Hour: 06
Day: *
Month: *
Weekday: *
Command: /usr/bin/archivemail --quiet --delete --days 10 /home/{USER}/mail/inbox

Make sure you replace {USER} with your actual cpanel username.
Hit the Commit Changes button and wait until sometime after 6:45 AM (assuming you set it up to run at that time) and login to your default email account to see if your emails have been deleted
If everything looks good your default inbox will now have any emails that are older than 10 days automatically deleted
To login into your default email account you use your cpanel username and password

If you wanted to have all the emails deleted that are older than three days you would simply change the --days option to 3

If you wanted to have all emails inside your mail directory including sent mail, spam, etc. that are older than 30 days deleted...
/usr/bin/archivemail --quiet --delete --days 30 /home/{USER}/mail/*

If you had an email account named info @ yourdomain.co.uk and wanted to have all the emails in that inbox that are older than seven days deleted...
/usr/bin/archivemail --quiet --delete --days 7 /home/{USER}/mail/{yourdomain.com}/info/inbox

If you had an email account named info @ yourdomain.co.uk and wanted to have all the emails in your sent-mail folder that are older than twenty-one days deleted...
/usr/bin/archivemail --quiet --delete --days 21 /home/{USER}/mail/{yourdomain.com}/info/sent-mail

Don't forget to change {yourdomain.co.uk} to your actual domain name !

You can look in your mail directory via your ftp client or the online file manager to see where your mailboxes are located.