Assume that you install the Cumulative Update 3 for Microsoft Exchange Server 2019 or Cumulative Update 2 for Exchange Server 2019 in a hybrid environment that has an Edge server installed. When a certificate is configured for the respective send connector, the Set-SendConnector cmdlet doesn't work, and you receive the following error message:
"PowerShell failed to invoke 'Set-SendConnector': Error 0x5 (Access is denied) from cli_GetCertificate"
"Error 0x6ba (the RPC server is unavailable) from cli_GetCertificate"
This issue occurs because the TLS certificate check (in case the TlsCertificateName attribute is populated on the send connector) doesn't work against the Edge servers as the RPC communication is blocked against the Edge servers.
To fix this issue, install one of the following updates:
For Exchange Server 2019, install the Cumulative Update 4 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.
The Hybrid Configuration Wizard (HCW) can successfully create the "Outbound to Office 365" send connector if it doesn't exist, as the New-SendConnector cmdlet can be used without issues.
Further changes (using the Set-SendConnector cmdlet) of the "Outbound to Office 365" send connector after the creation aren't possible.However, the "Outbound to Office 365" send connector can be deleted and recreated by using the desired configuration.
Microsoft has realized this problem and will post more information in this article when it becomes available.