Deleting Excess Disk Usage

[30feb]

I've got 60 Domains in Plesk. Some of the domain are exceeding Disk Usage Limits. Most probably the reason behind this is Email Data. I need to delete this Excess Disk Usage Data. I had also re-created the email accounts by deleting the accounts, but still it is showing the same amount of data. How can I Delete this excess data usage.
Thanx!