I have run into this issue at a number of my customers that utilize an Exchange Edge Server in their Hybrid Deployment. They’ll need to modify their send connectors for their forced TLS communication with their partners or own mailboxes in Office365. Whenever they want to modify the send connector and save the changes, they get the following error messages:
“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.
Now the current workaround for this has been to delete the Edge Send Connector and recreate the connector from scratch via PowerShell with all the settings and changes entered. This is not a viable solution especially if your communications with your partners change constantly and changes are made to the secure communications channel between you and them.
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.
For Exchange Server 2016, install the Cumulative Update 15 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
For Exchange Server 2013, there is no fix at this time. My personal recommendation is to plan an upgrade to Exchange 2019.