This error message indicates that your server cannot connect to smtp.gmail.com using the protocol “ssl://” over port 465. This could be a server configuration issue, or a network configuration issue, or perhaps a different setting would give you access to Gmail.
You’ll want to check with your system administrator or hosting provider regarding your server and network configuration to ensure your server has outbound access to smtp.gmail.com.
See this thread for additional troubleshooting options: