I am currently working on an email server that when it receives an email it will it add it to a queue, and if it fails to be sent it can then get retried and also based on what it receives sends an auto reply message.
What I am looking at being able to do, is the email server can also be an smtp server, so the user could configure, let's say php or another email client use my email server smtp and it can receive the message and then process it.
Is this something that is possible and how can I get it started, haven't found that much help on Google, it needs to work with mono (linux) and normal .net (Windows).
Thanks for any help you can provide
Here are examples of SMTP server implementation in C#:
Create a simple SMTP server in C#
SMTP and POP3 Mail Server
来源：https://stackoverflow.com/questions/11457722/creating-an-smtp-server-c-sharp