用SMTPClient检查邮件是否在VB.NET中成功发送(Check if mail was successfully sent in VB.NET with SMTPClient)

 我正在尝试创建一个将电子邮件发送到smtp服务器的应用程序。 
 
 服务器未设置为固定，但会根据电子邮件应发送到的电子邮件地址的域部分进行查找。 
 
 例： 
 
 发邮件至：test@stackoverflow.com 
 
 域部分：stackoverflow.com 
 
 MX记录查找的结果（命令行“nslookup -type = mx stackoverflow.com”： 
 
 
 
 MX首选项= 30，邮件交换器= stackoverflow.com.sgb.compsoverflow.com MX首选项= 40，邮件交换器= stackoverflow.com.s9b2.psmtp.com stackoverflow.com MX首选项= 10，邮件交换器MX preference = 20，邮件交换器= stackoverflow.com.s9a2.psmtp.com 
 
 
 知道邮件服务器是否接受邮件并且邮件已成功发送将非常有用。 
 
 到目前为止，我能够通过使用System.Net.Mail.SMTPClient对象及其SendAsync函数获取SMTP-Server错误代码（如果发生错误（StatusCode 5xx）），那么，如果有错误，我在SMTPClient的回调事件中获得一个Exception-Object 
 
 我很清楚，并非每个邮件服务器都会告诉我mailaccount是否真正存在，然后用错误代码拒绝我的邮件，而只是接受邮件并删除邮件。 因此，我会很感激另一种方法来检查邮件是否被发送（注意：没有阅读，这将是阅读确认） 
 
 最终目的是：尝试使用域名mailserver向收件人发送电子邮件，如果失败，请根据错误代码（用户不存在 - > abort / mailserver未响应 - >使用另一个邮件服务器（如果可用））继续操作。 
 
 预先感谢（并对错别字:)）） 

I'm trying to create an application that sends an email to an smtp-server.
 
The server is not set fixed, but will be looked up according to the domainpart of the email-address where the email should be sent to.
 
Example:
 
Email To: test@stackoverflow.com
 
Domain-Part: stackoverflow.com
 
Result of a MX-Record Lookup (commandline "nslookup -type=mx stackoverflow.com":
 
 
 
stackoverflow.com MX preference = 30, mail exchanger = stackoverflow.com.s9b1.psmtp.com stackoverflow.com MX preference = 40, mail exchanger = stackoverflow.com.s9b2.psmtp.com stackoverflow.com MX preference = 10, mail exchanger = stackoverflow.com.s9a1.psmtp.com stackoverflow.com MX preference = 20, mail exchanger = stackoverflow.com.s9a2.psmtp.com
 
 
It would be quite useful, to know if the message was accepted by the mailserver and the message was successfully sent. 
 
What I am able so far is, that I can get the SMTP-Server error code (if there was an error (StatusCode 5xx) by using the System.Net.Mail.SMTPClient Object and its SendAsync Function. There, if there was an error, I get an Exception-Object in the Callback-Event of the SMTPClient
 
I'm well aware that not every mailserver will tell me if the mailaccount truly exists and then reject my mail with an errorcode but instead just accept the message and then delete it. Therefore I would be grateful for another Method to check if the mail was sent (note: not read, that would be the read confirmation)
 
The final purpose would be: Try to send an email to a recipient using it's domains mailserver and if it fails, proceed according to the errorcode (user does not exist -> abort / mailserver did not respond -> use another mailserver if available).
 
Thanks in advance (and sorry for typos :))

原文：https://stackoverflow.com/questions/6679766