SMTP via .NET program failure

I have a program that handles vacation/sick requests which was recently moved from Server 2003 (IIS 6) to a new Server 2008 (IIS 7.5)

The notification email for when a user requests absence is no longer functioning.
 - It does however work for domain administrators!

I can ping and Telnet to the SMTP server which led me to believe it was a permission issue.
-I tried creating a new mailbox (Requests@domain) with everyone having full access permission
-I created a new receive connector allowing anonymous connection from the server IP




The program (SMTP Piece):

Dim email As New System.Net.Mail.MailMessage()
Dim client As New SmtpClient
client.UseDefaultCredentials = False
client.Credentials = New System.Net.NetworkCredential("username", "password")
client.DeliveryMethod = SmtpDeliveryMethod.Network
client.Host = AppSettings("SmtpServer")
email.From = New MailAddress("username@domain.com")
email.From = New MailAddress(AppSettings("EmailFrom"))
----------------------------------------------------------------------------------------------------------------------



This is the output if the user is not a domain admin:

[SocketException (0x277b): A system call has failed ***.***.***.***:25]
   System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) +273
   System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception) +584

[WebException: Unable to connect to the remote server]
   System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6) +8593522
   System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback) +8593954
   System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout) +3016971
   System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint) +286
   System.Net.Mail.SmtpClient.Send(MailMessage message) +1500

[SmtpException: Failure sending mail.]
   System.Net.Mail.SmtpClient.Send(MailMessage message) +2392407
   GlobalFunctions.error_email(String txtst, String txtmsg, String user) in C:\inetpub\wwwroot\Intranet\Requests\App_Code\GlobalFunctions.vb:114
   _Default.btnSubmit_Click(Object sender, EventArgs e) in C:\inetpub\wwwroot\Intranet\Requests\Users\Users.aspx.vb:401
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +155
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3804
RISLAAsked:
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Shaun KlineConnect With a Mentor Lead Software EngineerCommented:
Is the application pool for your web application running under the same credentials as was on the old server? From the error, it sounds more like the web application itself does not have permissions to access resources on your mail server.
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