如何使用C#仅从收件箱中获取未读邮件?

我需要从收件箱中收到未读的电子邮件-处理退回邮件.
我不需要完整的消息.我只需要:仅来自未读电子邮件的主题和正文.

我可能必须使用IMAP，因此可以向我推荐一个开源"的好解决方案吗?这样我就可以毫无问题地出售该软件了吗?

但是，当smtp服务器不支持IMAP时，我必须使用POP3吗? 那个项目对此有好处吗?或者，也许还有其他更好的方法?

感谢您的帮助，

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更新:
我有一个主意.
我可以阅读收件箱中有多少封邮件.所以，我也可以拿到最后一个.
我可以检查计时器中是否有退回消息(例如每5分钟一次).我可以一一收到消息，然后检查日期.如果消息是在5分钟前发送的，我会中断.
在这种解决方案中，我不会每次都从收件箱中收到所有邮件.那是一个好的解决方案吗?

我的想法的伪代码:

Hi, I need to get unread emails from my inbox - to handle bounce-backs messages.
I don''t need to get entire message. What I need is only: Subject and body only from unread e-mails.

I probably have to use IMAP, so could recommend me an "open-source" and good solution? so I can sell this software without any problems?

But, when smtp server don''t support IMAP, I have to use POP3? That project will be good for that? Or maybe there is some other, better way ?

Thanks for help,

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UPDATE:
I''ve got an idea.
I can read how many messages are in inbox. So, I also can get the last one.
I can check if there is a bounce-back message in timer (every 5 minutes for example). I could get messages one by one, and check the date. If the message was sent before 5 min ago, i would break.
In that solution, I will not get all messages from an inbox every time. Is that good solution ?

The pseudo-code of my idea:

TIMER( Tick every 5minutes )
{
    (LOCK)
    loop(on inbox from end to begin)
    {
        // If the message date is older then "5 minutes ago" break
        if (message date < DateTime.Now.AddMinutes(-5);)
        {
            if (the subject is "Undelivered Mail Returned to Sender")
            {
                // Here I will parse message so that I will know the addresse
                // And removie that addresse from my list.
            }
        }
        else
            break;
    }
    (UNLOCK)
}