When configuring a repository, you must specify retention policy that would be applied during analyzing source mailbox information before placing the actual mailbox item data into the repository. This approach allows you to decrease the amount of data transferred from source to target.
For example, if the retention policy is set to 3 years and you have configured a new backup job pointing at this new repository, this will work as follows:
- When you start a backup job, Veeam Backup for Microsoft Office 365 will first analyze the mailbox items metadata. In particular, it will check the last modification date for the item and calculate the item's "age". For example, a backup job is about to be running at 10:00 AM on September, 15, 2017, and last modification of an e-mail was made at 10:00 AM on September, 1, 2014. This means that the e-mail "age" is 3 years and 2 weeks.
- The "age" is then compared with the value that is set in the Retention policy for mailbox items for repository (3 years in our example). If the "age" exceeds the specified interval, then such email item will not be backed up into the repository. In our example, the e-mail item is older than 3 years, so it will not be backed up. On the contrary; an e-mail that was last modified at 11:55 AM on September 16, 2014, will be archived successfully.
This retention policy is then applied to the backup data in the target repository according to the following steps:
- After all suitable mail items are placed into the target repository, Veeam Backup for Microsoft Office 365 checks the retention policy application schedule. This setting defines how frequently Veeam should analyze the "age" of the mail data in the backup, comparing it with the specified threshold (a retention period), which is 3 years in our example.
- The retention period starting point is set to the current date/time. Obsolete data is removed from the repository automatically according to the following:
- An item will be removed from the repository if its "age" exceeds the threshold, that is, its retention period expired.
- A datastore will be removed from the repository when the last remaining items in the archive have their retention period expired, and no data arrives from the Exchange server by that moment.
A retention policy is applied to the backup repository, not to the backup job. Therefore, if you want your data to be processed by different backup jobs and to be preserved for a different amount of time, you should target each of these jobs to a different repository, having its retention policies configured appropriately.