email - Once I send an email, how much information can I get about its progress?

Question

I'm designing a capability to send emails out for my app.

I was wondering once I send out an email, is there anyway to find out whether

1. the email address exists and is real
2. the email was received
3. if not received, what the problem was? (mailbox full, email address invalid etc.)
4. the email was read (probably asking too much but would be good)

Do I get any feedback at all?

I'm using the SMTPClient in the .NET framework to do this.

Answer 1

1. 不。您可以查看目标服务器是否接受该地址。但是您无法确定该帐户是否真的存在。即使服务器接受该地址，它也可能在以后被退回。

2. 不。如果您没有收到退回邮件，则必须假设它已交付。没有保证。它可能已落入垃圾邮件箱等。

3. 如果未收到邮件，您将收到退回邮件（或者根据您发送邮件的方式，您在将邮件发送到目标服务器时直接在 smtp 事务中收到错误）。

4. 不。您可以请求阅读回执或做一些花哨的事情，例如嵌入指向外部跟踪器图像的链接。但是所有这些东西通常默认被阻止。