MetaLogix Professional Archive Manager for Exchange (PAM4Exchange) is a full-featured, enterprise-oriented, multi-tier application that provides a scalable and flexible archiving solution for Exchange.
It has a somewhat complex install that requires a variety of optional Windows Server applications such as MDAC, .Net, IIS, SQL Server (or Oracle) and the creation of user accounts, setting of permissions, editing of registry keys and so forth. Unlike the other n-tier apps, installing all the applications on the same hardware as the Exchange server is not supported (the others don't recommend this, but allow it for smaller setups and pilot projects).
The installation process is well documented, but the installer doesn't include a checker that will audit what has or hasn't been completed in the prerequisites. On the other hand, MetaLogix includes live installation support via phone or remote login if needed.
Once the installation finishes, importing the mail store for the initial archive and defining retention policies is simple, but with all the flexibility one might wish for. Searches finished quickly, and the search and restore through Outlook is transparent for users. Stubbing, finding and re-integrating PST files and configuring single-instance storage are all simple and straightforward.
The web portal makes accessing the archive for auditing or e-discovery a simple process. Roles can easily be defined to allow the appropriate rights to single mailboxes, groups or whole stores, with good Active Directory integration. It's easy to find and restore messages or entire mailboxes, create searches, export messages to a PST or other type of data file, and to place legal holds on messages once they're found. PAM can also migrate messages from one version of Exchange to another, or from Exchange to SharePoint. Other PAM products provide archiving of Windows files and SharePoint servers.
PAM offers a complete enterprise archiving solution with prices somewhat lower than Symantec at large numbers of users. As with Symantec, SMBs will find that even at comparable prices per user, the complexity of setup and administration keeps PAM from being a perfect fit. For larger firms, the excellent scalability and flexibility make it definitely worth consideration.