As most important part the BranaBox contains a full email provider.
Every mail is save as single file, which isn't changed anymore. You can open these email files with any other application and include into your backup strategie.
Mail accounts of more than 100,000 mails and 100GB size are no problem at all and are being used. After an initial indexing all mails are available immediatelly. Even web access over the old GSM-Network (or with exhausted high-speed-volumne) is sufficently enough. We don't need hour glasses in our user interface.