In Microsoft Exchange Server 2019 or Exchange Server 2016, when the organization forms library has more than 500 items and an Outlook client user selects Choose Form, a new restriction is created. This causes a notification to be sent to every open Outlook client. Those clients then do several remote operations (ROPs) through RPC protocol against the public folder mailbox to see what changed. The additional load from this activity causes a performance and connectivity issue in the Outlook clients.
Note This issue doesn't occur in Exchange Server 2010.
To fix this issue, install one of the following updates.
Exchange Server 2019
or a later cumulative update for Exchange Server 2019
Exchange Server 2016
or a later cumulative update for Exchange Server 2016
Learn about the terminology that Microsoft uses to describe software updates.