System.Net.Mail.SmtpFailedRecipientsException

I'm migrating my existing application to a new application server. When test on the suggestion box which involve SMTP, i get below error message:



System.Net.Mail.SmtpFailedRecipientsException: Unable to send to all recipients. ---> System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: No such user here --- End of inner exception stack trace --- at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message)

Few things that i test on new server:

1. Install SMTP - check on document provided
2. Testing with the Pickup directory
   You can also compose a simple e-mail text file based on the SMTP specifications (RFC 822). Here is the content of a sample text file typed in Notepad:
   
   From: myname@mydomain.com
   To: someone@somedomain.com
   Subject: testing
   This is the test message body.
   
   Simply copy or move the text file into the Pickup directory where SMTP was installed. (The default path should be "\Inetpub\mailroot\Pickup" but if you have Exchange installed then the path will be "\Program Files\Exchsrvr\Mailroot\Vsi 1\Pickup".)
3. Set Relay Restrictions in the IIS admin. Put your app server IP Address/Domain Name in the Relay Resctictions.
   
   
   
4. After all, remember to restart your machine. Restart IIS or Virtual SMTP server won't help. Restart the server do the best.

Done