相關說明
https://support.google.com/a/answer/81126?visit_id=638670617790772876-310686913&rd=1#authentication%C2%A0d2e1a72fcca58-72407a1a6c8si1
首先防火牆都要打開
SMTPs
tcp 465 SSL
tcp 587 TLS
tcp 25 STARTTLS
還有 Mail Server 都要開啟
SSL+TLS