Exchange 2013, CU5.
Hi,
I have frequent logs showing 36875, reporting "The remote server has requested SSL client authentication, but no suitable client certificate could be found. An anonymous connection will be attempted. This SSL connection request may succeed or fail, depending on the server's policy settings."
I would like to work out which server is making these requests, and also which certificate is being offered but deemed 'not suitable'.
I have increased the logging level to "7" for HKLM\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\"EventLogging" but this only provides informational events to say for TLS1.0 and TLS1.2 that "SSL server handshake completed successfully".
I am running an all-in-one Exchange server. I have two receive connectors (one for inbound mail from Mimecast and the other for relaying emails from internal applications) both of which have the FQDN which matches my public certificate. I still have the self-signed cert on the server. Mimecast attempts to deliver mail using opportunistic TLS, which is working - the headers I receive from a gmail address show TLS being used at all hops.
Any help gratefully appreciated.