Deepinvent MailStore is a software-only product designed for small and mid-sized businesses.
With no separate database server, installation is simple. MailStore supports a wide variety of mail servers in addition to Exchange, and can also work directly with email clients such as Outlook, Outlook Express, Windows Mail or Thunderbird, if clients are accessing a hosted email server off site. It can also archive data from PST files or other email stores such as MBOX or EML files. The system can also archive files stored on a Windows PC or server. An Outlook plug-in makes retrieving archived messages easier.
For accessing the archive, the usual web portal and Outlook plug-in are supplemented by a separate Windows application and even an iPhone app. Search functionality is good, though not as flexible as some, with the search form relying on check boxes and drop-down menus rather than fields that let you specify custom search parameters.
Performance on searches was good. And MailStore supports migration of mail from one version of Exchange to another, or from one email client to another.
MailStore does not include the more sophisticated features such as role-based administration, policy enforcement or legal holds. However, with low prices, a very simple installation and excellent ease of use, it is a good fit for small businesses in which the time to learn a more complex system is not available and basic archiving is all that is desired.