Warning: stream_socket_enable_crypto(): SSL operation failed with code 1. OpenSSL Error messages: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed in Drupal\smtp\PHPMailer\SMTP->StartTLS() code example

Example: stream_socket_enable_crypto(): ssl operation failed with code 1. openssl error messages: error:1416f086:ssl routines:tls_process_server_certificate:certificate verify failed

Try changing the app/config/email.php
smtp to mail