All OIT mailbox servers are backed up regularly in case of catastrophic server failure.
IMAP Email: OIT does not provide a service specifically for restoring email that you delete from the server intentionally or by accident. Mail lost due to server/system failure will be restored. Mail lost through user error or deletion we will do our best, but we can not always guarantee the emails will be there.
You should regularly back up any email messages that you do not want to lose. To back up messages stored on the mail servers, copy them to your local machine or network drive, using an email client, and make sure they are included in the backup process. For more information on how to backup your email please see the help files for your email client.
Google provides instructions on how to backup email stored in Gmail here
Please make sure that important email messages residing on your local machine are included in your backup process.