用System.Net.Mail发送邮件时错误信息  

配置示例如下：

<appSettings>
        <add key="EmailFrom" value="emanxaut@xaut.edu.cn"/>

        <add key="EmailTo" value="eman@xaut.edu.cn"/>

        <add key="SmtpServer" value="mail.xaut.edu.cn"/>

        <add key="Port" value="25"/>

        <add key="MailUser" value="emanxaut"/>

        <add key="MailPassword" value="xxxxx"/>

        <add key="NeedCredential" value="true"/>

        <add key="EnableSSL" value="false"/>    </appSettings>

配置错误及提示信息:

SmtpServer错误：

  Unable to connect to the remote server

Port错误：

  Unable to connect to the remote server

MailPassword错误：

  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.

MailUser错误：

  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. 

EnableSSL错误：

  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. w12sm2503911tib.10

EmailTo错误：

  仍然可以“成功”发送，无错误提示。

EmailFrom错误：

  仍然可以“成功”发送，无错误提示。

NeedCredential错误：

  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.