详细的错误信息如下：

发送邮件出错:发件人webmaster@58vip.com 收件人：webmaster@58vip.com信息：The message was undeliverable. All servers failed to receive the message ClientLogging enabled: Client Remote Address: 219.150.228.130 .execute() { Trying server mail:smtp.58vip.com <- 220 ESMTP on WinWebMail [3.7.0.5] ready. http://www.winwebmail.com -> EHLO web-master <- 250 SIZE -> AUTH LOGIN <- 502 Error: command not implemented Authentication failed. smtp.58vip.com failed.. No socket for server. ConnectToServer() 1 of 1 servers failed }

原因是，你有WinWebmail中，没有"启用SMTP发信认证功能"，请选中它。
可以在服务器上，开始菜单中，启用Winwebmail控制台，然后右键点系统设置