MailSift is an always on, automatic mail protection service that is completely managed for you!

Email is routed through MailSift to work behind the scenes to quarantine spam, and email viruses before they reach your Mailbox. By simply re-directing the mail exchange (MX) record through the MailSift servers, email traffic will be scanned before entering your network and thus reducing the load on your Mail Server and local email client.

No hardware or software to install.
No changes to your existing email client program (i.e Outlook, Thunderbird, Apple Mail). Centralized management for Administrators.
Each Mailbox user can set their owns own Spam sensitivity settings and manage their WhiteLists