RedGate Exchange Server Archiver (ESA) uses flat files rather than a SQL server, but nonetheless provides deduplication of messages in the archive, along with good search features, stubbing of messages in Exchange, integration with Active Directory and a simple administrative interface.
Installation does have a number of prerequisites, including creating user accounts and installing Windows options such as .Net, MAPI, IIS and ASP.NET. Once that is all done, the installer is quick and simple to run. Configuration is also very simple, there are four archiving options, archiving the whole message but leaving the originals on the Exchange Server, archiving just attachments and leaving the originals on the Exchange server, archiving attachments and removing the originals from the Exchange server, and archiving the message and attachment and leaving only a stub on the Exchange server.
Rules defining which messages to archive are easy to create, but everything that is archived is treated the same way – there is no way to archive and stub messages and attachments for "marketing" and archive just attachments for "engineering". The end user experience is transparent with or without the Outlook plugin, and searches ran quickly, with flexible search criteria.
ESA is focused on archiving for disaster recovery and fault tolerance rather than compliance or e-discovery. Search tools for the administrator exist, but exporting e-mails found in a search is relatively cumbersome, and there is no specific legal hold function. ESA administrators must be domain administrators in Active Directory.
All emails archived are retained for the life of the store, there is no policy to expire messages and remove them, the only way to remove messages is to create a new store and disconnect the old one. This is not necessarily a negative, depending on the types of regulations you are trying to comply with – a number of standards require a write-once, read-many (WORM) type of archive. ESA also makes it quite simple to move all messages in an archive back to the Exchange server, making it relatively easy to uninstall and remove the product.
With a simple experience for both users and administrators and a low price for small organisations, ESA is a plausible fit for organisations that need a WORM archive.