We've just made the latest version of MailStore live on our site and if you, or perhaps your customers, are users of Google Apps, it's one I highly recommend you download.
The ability to archive Google mail isn't completely new to MailStore, however in previous versions, each mailbox would need to be archived individually, requiring a separate archiving 'job' and manual entry (and ongoing maintenance) of username and password credentials.
In version 9.1, the German developer have now made the whole process a breeze.