Roller Network

Paid accounts are recommended e.g. for 100MB of mail. If there aren't hard limits, how do you "force" customers to change to higher accounts?

I am using a free basic account. It is recommended to use this account type with less than 2MB of mail per day. Normally the Rollernet Secondary MX receives 0MB of mail for me. Actually my primary mail server was not down for over two years. But if he goes down there will be much more than 2MB for s...