ASP.Net EMail, Rejects Recipients

Dear Forum and Tech Support:

I have an ASP.Net page that sends eMail, which has been working for months. It uses the code recommended by Winhost support. However, it stopped working recently and gives the following error:

"Mailbox unavailable. The server response was: <Recipient Name> No such user here"

Anybody come across this issue? Any ideas? Unless the recipient is the postmaster account, it rejects any valid email addresses in the To, Cc, or Bcc line.

Thank you.
Robert Greiff

 

Dear Winhost staff:

I see the same problem from khalilim on 9/21/2009, but it doesn't look like there was any resolution. http://forum.Winhost.com/showthread.php?t=65 Did anyone figure this out? Strangely, the code was working when I first installed it on Winhost, but recently started sending the error.

 

Dear Elshadriel:

Thank you for your response. Yes, I am passing authentication. Here is the relevent code. Please let me know if there is any other issue you believe may be causing the problem. As I said, the code was working for several months.
Thank you.

Robert Greiff

Dim oMail As New System.Net.Mail.MailMessage(addrFrom, addrTo)
With oMail
.Subject = Me.txtSubject.Text
.Bcc.Add(addrBCC)
.BodyEncoding = Encoding.Default
.Body = strBody
.IsBodyHtml = True
.Priority = Net.Mail.MailPriority.Normal
End With
Dim smtpCli As New System.Net.Mail.SmtpClient(SMTPServer)
Dim basicAuthenticationInfo As New System.Net.NetworkCredential("[email protected]", "rg3653rg")
smtpCli.Host = "mail.reevepeermentor.org"
smtpCli.UseDefaultCredentials = False
smtpCli.Credentials = basicAuthenticationInfo