How to send SMTP email using vb.net - error 5.7.1 Unable to relay

Question

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I am trying to send an email using vb.net 2008 via our corporate exchange server and I am receiving the following message. Mailbox unavailable. The server response was: 5.7.1 Unable to relay for MyEmailAdrress@MyDomain.com. The email addresses are mine for the corporate domain, and the login credentials are mine for the domain. I have not tried to send email outside of the domain thus i don't understand the RELAY part.

Thanks.

Ed

Try
       ' Create a new MailMessage object and specify the "From" and "To" addresses
       Dim message As New MailMessage("MyEmailAdrress@MyDomain.com", "MyEmailAdrress@MyDomain.com", "Subject HERE", "Body message HERE")
       Dim emailClient As New SmtpClient("MySMTPServer.MyDomain.local")
       ' Authentication
       Dim basicAuthenticationInfo As New System.Net.NetworkCredential("MyNetworkUSERID", "MyNetworkUSERPASSWORD", "MyDomain")
       emailClient.UseDefaultCredentials = False
       emailClient.Credentials = basicAuthenticationInfo
       message.IsBodyHtml = True
       emailClient.Send(message)
   Catch ex As Exception
       Debug.Print(ex.Message)
   End Try

Below is the OUTPUT

VB

Mailbox unavailable. The server response was: 5.7.1 Unable to relay for MyEmailAdrress@MyDomain.com

Posted 3-Feb-14 9:46am

TheITManager

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Comments

Richard C Bishop 3-Feb-14 15:49pm

You have to use actual data to send an email. Real SMTP client and what not.

TheITManager 3-Feb-14 15:58pm

I am using REAL smtp information. The above code is just an example. The actual code I am using for my corporate application contains the name of my corporate smtp server, my actual email address, username, passowrd etc...

Richard C Bishop 3-Feb-14 16:00pm

lol, well we can rule that issue out then.

mgoad99 3-Feb-14 18:26pm

I have a few applications that have used SMTP to send an email to a local SMTP server inside my domain. I also send email within the domain. For me, I had to go onto the box that was setup as the SMTP server and add the IP address of my PC (where i was testing) and any other PC or server that is sending the mail. In the properties for the SMTP server there are relay restrictions. I added the ip addresses i need there.

If that is the problem, here is an article that may help
http://technet.microsoft.com/en-us/library/aa996446(v=exchg.65).aspx

I hope that helps or at least points you in the right direction. Good luck!

TheITManager 4-Feb-14 14:19pm

ANSWER!! Had my development laptop's IP address added to the ALLOW RELAY list on the mail server. -- This resolved the problem, and as it turned out every block of EMAIL code that I had tested and failed before all now work, atleast from my PC. I am just curious as to how to expand upon this. What i was not understanding was that I was using a valid network user id and password for the domain, and it too was failing. Thanks for the feedback! Ed

2 solutions

Solution 1

Try this code making necessary changes.

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
      Try
          Dim Smtp_Server As New SmtpClient
          Dim e_mail As New MailMessage()
          Smtp_Server.UseDefaultCredentials = False
          Smtp_Server.Credentials = New Net.NetworkCredential("username@gmail.com", "password")
          Smtp_Server.Port = 587
          Smtp_Server.EnableSsl = True
          Smtp_Server.Host = "smtp.gmail.com" //Replace with your domain host name.

          e_mail = New MailMessage()
          e_mail.From = New MailAddress(txtFrom.Text)
          e_mail.To.Add(txtTo.Text)
          e_mail.Subject = "Email Sending"
          e_mail.IsBodyHtml = False
          e_mail.Body = txtMessage.Text
          Smtp_Server.Send(e_mail)
          MsgBox("Mail Sent")

      Catch error_t As Exception
          MsgBox(error_t.ToString)
      End Try

   End Sub

Posted 3-Feb-14 21:39pm

Vamsi Krishnna

Comments

TheITManager 4-Feb-14 10:20am

I am trying to use Exchange server smtp..
This returns error:

System.Net.Mail.SmtpException: Failure sending mail. ---> System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 11.70.30.80:587

Vamsi Krishnna 4-Feb-14 10:43am

Check if the ports are active and listening on the target machine(server port-587 in above case),if not configure the firewall on target machine to listen on that port.

Vamsi Krishnna 4-Feb-14 10:48am

Check this list for different ports on exchange and their functionality.

https://support.prolateral.com/index.php?/Knowledgebase/Article/View/179/0/what-ports-does-ms-exchange-use

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

TheITManager · Accepted Answer · 2014-02-04T08:24:00

ANSWER!!

Had my development laptop's IP address added to the ALLOW RELAY list on the server. -- This resolved the problem. When I deploy this onto a production server I will have to get the servers IP address added also.

Thanks to mgoad99 http://www.codeproject.com/script/Membership/View.aspx?mid=3894223[^]

UPDATED VB CODE NO LONGER REQUIRES USER NAME, PASSWORD or DOMAIN

VB

 Dim MailFrom As System.Net.Mail.MailAddress
 Dim MailTo As System.Net.Mail.MailAddress
 Dim MailSubject As String
 Dim MailBody As String
 Dim Mail As New MailMessage
 Dim MailClient As SmtpClient

 MailBody = "Test Email"
 MailSubject = "Test Subject"
'Here I do not care about the from Email address, it is a Dummy-Email made up
 MailFrom = New MailAddress("DUMMY-Email-Here@SomePlace.com")
 MailTo = New MailAddress("JDoe@SomePlace.com")

 Mail.From = MailFrom
 Mail.To.Add(MailTo)
 Mail.Subject = MailSubject
 Mail.Body = MailBody

'25 is the port of the SMTP host
 MailClient = New SmtpClient("MySMTPServer.someplace.local", 25) 

 Try
     MailClient.Send(Mail)
 Catch ex As Exception
     Debug.Print("Mail Error: " & ex.Message)
 End Try

How to send SMTP email using vb.net - error 5.7.1 Unable to relay

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How to send SMTP email using vb.net - error 5.7.1 Unable to relay

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