Mail Folder

Just installed WP with a web site up and running
I keep getting Disk Space warning from my Control Panel, that my 500Mb allowance is near full
When I look at Disk Manager I find the MAIL folder is reading 179Mb
public_html folder is approx 300Mb
However, I have emptied/purged all the mail boxes ( Trash/send) etc but this figure still remains
So is the 179Mb correct for an empty mail box ?