Email constantly offline

My Company experiences a lot of days with the mentioned internet service provider where our emails are offline. Our emails have been offline today from 07:00am and is still offline now at 15:00pm. This is totally unacceptable as my company relies on emails for sales and orders. The Support centre only passes the buck and cannot give me time/date of when our internet will be back online. i cannot accept that in this day and age we have to be without our email system for a whole day.