Exchange Modern public folders and how-to cope with them.

With Exchange Hybrid public folders there is two options, either Legacy or Modern.

You always have to migrate them to the cloud either thru Exchange Hybrid (13,16 and 19) and Exchange Hybrid (10) or with Third-party tools.

If You have to stay in a Hybrid mode there could be trouble with clients logging into public folders and here is Microsoft Support step-by-step instructions for these problems.

There is also set-CasMailbox and Set-Organizationalconfig cmdlet’s that could be very useful:

• PublicFolderClientAccess is an optional parameter on the user object. By default, its value is set to ‘false’. Setting this to ‘true’ on a specific user designates this user as one of users who will see public folders in Outlook.
• PublicFolderShowClientControl parameter on the organization config. By default, the value of this parameter is also ‘false’ and once it is set to ‘true’, the controlled access of public folders is enabled.

One user:

All Cas Mailboxes:

Enable config on Organizational config:

For onpremise Exchange environments it will be available from Exchange 2019 CU2 and Exchange 2016 CU13.

And if You want a user to login easily without double prompts from Exchange Online Outlook WebApp to Onpremise Outlook Web Access use this one.

https://docs.microsoft.com/en-us/exchange/hybrid-deployment/simplify-owa-url

And as a final note, You should be absolutely migrating PF’s to Microsoft 365 groups -> Here’s how.

It’s easy to create individual groups from Public folders.