文章目录

• 1 概述
• 2 协议类型
• 3 网工软考真题

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// 2022年 上半年 上午 第30、31题
1. 电子邮件客户端通过发送对（30）服务器的（31）端口的 TCP 连接进行邮件发送(30) A.POP3   B.SMTP   C.HTTP   D.IMAP(31) A.23     B.25     C.110    D.143// 参考答案 30=B, 31=B