For the past 8 days, all of our email servers were not able to send out emails and one server in particular was being used to send out 200 spam emails daily.

This server has been permanently shut down. We have decided to migrate all our website and email hosting to our own new servers dedicated only to our usage.
There will be a delay of a few days as we move all our data across and hopefully, all should back to normal by mid next week.