Migration to Modern Public Folders - Notes from the Field

Thanks for the Notes from the Field!

I have a particular challenge migrating from Exchange 2010 Public Folders to Exchange 2013 modern Public Folders. The issue is that our Public Folders were created in a child OU, not the root level. Our plan is to mail disable and re-enable them after we have unlocked (step 7) our Public Folders so they get recreated in the root. My concern is what happens to the mail in the queue when the mail-enabled Public Folder gets disabled? Will it NDR immediately, or is it a question of how long it takes to before the next retry of a given piece of mail? If it's the latter, can we increase the retry length temporarily or do we have to force the retries in the queue and wait until all the queues clear? Any thoughts on how to mitigate this risk would be appreciated.