Mimecast offers its technologies as an appliance and a managed service for smaller enterprises, run from three data centers. The service is almost wholly automated, with clients not expected to do much admin work at all beyond reporting.
The service starts by watching regular outbound mail for a few days to build up a whitelist of email senders known to be valid recipients. Incoming connections are compared to that whitelist so invalid recipients can be filtered, but this needs careful handling for those mail aliases and service accounts that do not generate outbound mail. Indeed, it is probably better served by just integrating with an LDAP server, which the service does support anyway.
Incoming mail is treated in a similar way — if the sender and recipient have not communicated before, it is briefly quarantined while checks ensure the sender is a real mail server rather than a bot. In practice, this should avoid false positives on spammy-looking valid mail-like newsletters.
With no intervention required from users, we were expecting a very simple management GUI, but were astonished at what is actually provided.
Mimecast offers an amazing degree of control over the operation of the service, with policy options on every aspect of mail delivery, handling and management. The array of controls is daunting, but presented in a very effective interface that even includes a fully fledged web mail client.
A massive array of controls can be enforced on message headers and attachments, but there is very little capability for actual filtering on message bodies. This alone lets the service down.
All access is logged, meaning that firms with concerns that mail administrators might access emails they should not can easily conduct audits to check that no inappropriate activity has occurred.
Mimecast deserves kudos for its extensive controls and features. It might be new to the scene, but it has built a product worthy of attention. Unlike many others, 24x7 support is included without extra charge, and long-term archival is part of the service.