Failure Sending Mail in C# SMTP server

Question

I am writing web services for an application in which there is a registration function and upon registration i have to send an email through the server. i have already done this kind of work for another website with Parallel Plesk server. using the same code i'm trying to send email but getting this exception. I searched Google and some related answers here but all in vain. Help?

"System.Net.Mail.SmtpException: Failure sending mail. ---> System.Net.WebException: The remote name could not be resolved: 'domainname.com'\\r\\n at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6)\\r\\n at System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback)\\r\\n at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback)\\r\\n at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)\\r\\n at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)\\r\\n at System.Net.Mail.SmtpTransport.GetConnection(ServicePoint servicePoint)\\r\\n at System.Net.Mail.SmtpClient.GetConnection()\\r\\n at System.Net.Mail.SmtpClient.Send(MailMessage message)\\r\\n --- End of inner exception stack trace ---\\r\\n at System.Net.Mail.SmtpClient.Send(MailMes sage message)\\r\\n at ActivityTracker.Controllers.ValuesController.parentRegistration(parent p) in c:\\Users\\Harris\\Documents\\Visual Studio 2012\\Projects\\ActivityTracker\\ActivityTracker\\Controllers\\ValuesController.cs:line 89"

Answer 1

From the machine running your code:

• You CANNOT resolve domainname.com
• You CAN resolve to the IP address of domainname.com

This indicates that you are missing an internal DNS entry.

As your machine can talk to the IP but not using the DNS name - you can work around the issue by creating a Hostname entry for the domain name in question.

Here's how to modify your Hostname file:
http://www.rackspace.com/knowledge_center/article/modify-your-hosts-file

Once this entry is in place, you should now be able to ping to domainname.com . When that works - rerun your code.

Some useful DNS reading:
http://www.techrepublic.com/article/understanding-how-dns-works-part-1/
http://social.dnsmadeeasy.com/blog/understanding-dns-forwarding/

NOTE: You've not confirmed if you can telnet to the port in question, so I am presuming this is ok - ruling out any firewall issues.

Answer 2

尝试使用 GMail SMTP，如果它与 GMail SMTP 一起工作，那么您指定的域存在问题。