IMAP data is replicated to independent systems and storage at application level.
Snapshotted encrypted ZFS filesystems are also replicated to external out-of-band storage to allow for desaster recovery.

If you have (accidently) deleted your messages / mailboxes postmaster might be able to restore them.
Please send an email to postmaster@iai.uni-bonn.de using our mail service and authenticated with your computer science account.
To speed-up the process name the criteria - let us know what you did and what you want back:

• what folders and/or messages
• what time in the past
• whatever might be helpful