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.