Generate a list of emails in Exchange 2013 deleted more than 90 days agao

The problem with that is logs are kept for 30 days by default, and actual deleted mail items are kept for 14 days by default, do if all the default options are used then there is no way to retrieve that information. You will need to review the retention policies on the mailbox DBs and see how long mail is retained after being deleted but by default it's 14 days, and the logs which doesn't show anything about deleted items are 30 days by default. Possible you may be out of luck on that request.

Maybe what you're taking about is just running the IMAP EXPUNGE operation, which physically removes deleted files.

To do this, you'll just write some simple code to connect to your IMAP server using some sort of system admin privilege, walk through all accounts + all folders + issue an EXPUNGE.

Some mail servers allow a non-standard recursive EXPUNGE in all folders for a given user.

You'll have to dig into the depths of full IMAP syntax Exchange supports.

Note: Exchange docs contain long discussions about setting retention policy. There is no message of how to set any type of EXPUNGE policy.

The original mail policy was to never remove items from deleted items.  Lots of users deleted mail from their mailbox but never removed it from Deleted items.  They have recently requested a change to the policy but want to see how much is actually out there and a way to verify that the new policy is working.

Thanks for the suggestion but I have already used Get-MailboxFolderStatistics to generate a report for all mailboxes showing the size of each folder but that wasn't what they were looking for.   I need to list deleted items by user by date if possible.

Not possible.