Email disk quota
From mail2web.com Wiki
The mail2web.com hosting plans include a fixed amount of disk space. However this is a soft cap and we will allow your account to use more than your quota. If we were to enforce a hard quota, this would prevent you from receiving any further emails to your account.
If your account exceeds your disk space quota, we will bill you at a rate of $0.20 per MB per month for the overage. If you want to ensure that your account doesn't exceed your quota, you can set maximum mailbox sizes for each user on your domain. You can access these options from your email administration page.