Default WHM email sending will fail.
Connection failed. Error #2: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages:error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed #2061
You need to update setting
WHM under Home »Server Configuration »Tweak Settings »Mail.
Then the option Restrict outgoing SMTP to root, exim, and mailman (FKA SMTP Tweak) was set to Off.