log4net SmtpAppender 配置

https://www.cnblogs.com/smartstar/p/11588937.html

https://github.com/apache/logging-log4net/blob/master/src/log4net/Appender/SmtpAppender.cs

Nlog 配置
https://www.jb51.net/article/143002.htm

NLOG 邮件配置
https://www.cnblogs.com/ykbb/p/15226976.html