Client certificate questions

When the IMAP client begins the SSL/TLS session it will perform a handshake. What is the certificate that is sent from the client to the server during the “ClientHello” handshake message? Can you point it to me in the source code? For example, the certificate sent must be signed by a world acceptable Certificate Authority (CA) or it will be rejected by the mail servers. Any info is really appreciated as i’m doing research. Thanks!

Client certificates are an optional part of the TLS handshake (unlike server certs, which are generally mandatory). If you wish to use a client certificate, you need to supply it when setting up your account.