How can different retentions be implemented for Exchange Online Backups?
For example 30 days on primary copy, and 180 days on secondary copy.
One can create a Storage Policy / Plan with such retentions, but as Exchange Online uses dedicated Exchange Policies for retention, this won’t achieve the desired outcome.
A mailbox can only be assigned one Exchange Retention Policy, defining how long the messages are retained for after receiving them / them being deleted, but that will take effect on all assigned backup copies.
Due to size and cost limitations, having one retention for both copies is not an option unfortunately, so I’m wondering if this is possible at all.
One idea could be to run periodic full backups (archive but select “convert to full”) and then have the secondary copy on selective, only using the monthly fulls for example. But this will create massive overhead if we have to run a full backup of all Exchange Online mailboxes once a month or so. Plus, I don’t think with that would work though, as selective backup copies can only select full backups, and even a converted archive job to full would still show up as incremental, according to this post: Microsoft 365 Exchange Online - why only forever incremental backup? | Community (commvault.com)