Design

After selecting Amazon's S3 as the backup medium, a number of other factors were weighed and considered for implementation as a part of our backup solution. Here are some of the items that have made their way into the final design:

Application-specific components

• Duplicate prevention. Previously, changing IMAP message flags would cause a new copy of a message to be stored on the system. Message and folder information is now stored separately. This allows search indexes to be rebuilt very quickly after restoration.

Message backup

• Separation of backup job creation and backup job processing
• Running backup jobs during off-peak hours and with low system resources to prevent potential load issues
• Encryption using the high-trust AES-128 algorithm

Message restoration

• Restore all mail folders for a user, or just restore a specific folder
• Preview folder listings for any user inside the 14-day window for which backups are stored
• Obtain simple message counts for any user or for any individual folder
• Restore data to the original mailbox or to an alternate mailbox, as determined by the customer email administrator