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.