I have a unique situation to discuss. I am working on a plan to bring Mailboxes from Cloud back to On-premise. I need to set up greenfield infrastructure for Exchange and other collaboration tools. I have a couple of concerns and appreciate if you could help me on this.
Average Mailbox Size is 10gb
Almost 60% of users are above 10GB Mailbox and 98GB is the Highest one.
How do I migrate them back to On-premise? I know I cannot accommodate their current size back to On-premise. We are thinking of Mailbox size of 1GB back on-premise.
Why are you not able to accommodate the size? On-premises you can have mailboxes as large as you want, provided you have the hardware. Unless you want to deal with "archiving" to an external system, or even worse, PSTs.
You could apply stringent mailbox retention policies to remove and permanently delete all email older than (say) 3 months. That would reduce the size of the mailboxes to a manageable size. But I wouldn't do it without telling the users what you are going to do...