Autodiscover (public) DNS record in hybrid setup [Public Folders]

[Ivarious90]

Hi all,

We have a client with an Exchange 2013 hybrid setup. All the mailboxes are already in O365 (for already 2 years). I see that the autodiscover record is still pointed to the on-prem Exchange server instead of M365. Can we safely change this from on-prem to M365? 

The only thing the Exchange 2013 server is used for are the public folders. The company have 2 'large' email folder (100GB+).

Core question is; can we safely change the autodiscover record from on prem to M365 (or what things should we consider)?

And if someone have a good idea for the public folders so we can phase out the old Exchange 2013 environment, we would like to know :) 

Thanks in advance!

[#2]

@Ivarious90 
As soon as all client components that require AutoD are migrated to EXO, you can change the external DNS to use the EXO CNAME target.

Does EXO reference the on-premises public folder hierarchy as "external" and do EXO users have access to that hierarchy? In that case, you cannot change the external AutoD DNS resource record.

Why don't you migrate modern Ex2013 public folders to EXO?

-Thomas 

[#3]

@Thomas Stensitzki 

As soon as all client components that require AutoD are migrated to EXO, you can change the external DNS to use the EXO CNAME target. -> Clear, thanks

Does EXO reference the on-premises public folder hierarchy as "external" and do EXO users have access to that hierarchy? In that case, you cannot change the external AutoD DNS resource record. -> How can I check this? When I'm in outlook and navigate to the public folder structure, I see Public Folders - email address removed for privacy reasons.

For the migration I found this: https://docs.microsoft.com/en-us/exchange/collaboration-exo/public-folders/batch-migration-of-legacy...

2 of my public (root) folders are 100GB+. These are 2 root folders but have lots of sub folders....

Everyone in the organization have access to this folders (+/- 100 users). What is the best way to migrate these? (I already asked to clean-up the folders, but they have to keep this data..)