Cloud hosted email security is essential for any Exchange Server or any on premise mail server. Why would you want to take the risk of treating a virus in house?
There are many benefits to using a hosted cloud email filtering services, not only the reassurance that 100% of viruses are stopped before reaching your business network, by knowing that all emails are delivered from a single provider, all emails delivered direct from the Internet can be stopped at your firewall. This not only improves security but reduces the load on internal mail servers such as Exchange from not having to deal with the large volumes of spam emails sent every minute.
If you email server goes down due to power failure or Internet outage for example, emails are queued on the filtering servers so your customers do not receive emails that your service is down and once the server is restored emails will start coming in again including those sent during the down period.
We have been using Web Sense for many years and are familiar with their systems and have a good relationship with their administrators and will configure your content filter rules to block all threats and the majority of spam while limiting the valid emails that are stopped to a minimum.