We should use email-ca-bundle.crt for CA certificates

Makefile

@@ -231,10 +231,10 @@ tls_server_cert: /etc/ssl/private/server.pem
 tls_server_key: /etc/ssl/private/server.pem
 
 # File containing one or more Certificate Authority (CA) certificates.
-#tls_client_ca_file: /etc/ssl/certs/cyrus-imapd-ca.pem
+tls_client_ca_file: /etc/pki/tls/certs/email-ca-bundle.crt
 
 # Path to directory with certificates of CAs.
-tls_client_ca_dir: /etc/ssl/certs
+# tls_client_ca_dir: /etc/ssl/certs
 
 # The length of time (in minutes) that a TLS session will be cached for
 # later reuse.  The maximum value is 1440 (24 hours), the default.  A