CODEWITHSUNDEEP
asp.netvb.netemailsmtp
Uzair Khan
Uzair Khan

Reputation: 67

Authentication is required for relay

I am novice in asp.net and am trying to send email via this short code. 

 Public Class sMail
        Public emailBody As String
        Public emailSubject As String
        'Public sendTo As String

        Public Function sendMail() As Boolean
            Dim eMail As New System.Net.Mail.MailMessage
            Dim smtpClient As New System.Net.Mail.SmtpClient("mydomain", 25)
            Dim credentials As New System.Net.NetworkCredential("[email protected]", "password")
            smtpClient.Credentials = credentials
            smtpClient.UseDefaultCredentials = True
            smtpClient.DeliveryMethod = Net.Mail.SmtpDeliveryMethod.Network
            eMail.From = New System.Net.Mail.MailAddress("[email protected]", "Info")
            eMail.To.Add(New Net.Mail.MailAddress("[email protected]"))
            eMail.Subject = emailSubject
            eMail.Body = emailBody
            eMail.BodyEncoding = System.Text.Encoding.UTF8
            eMail.IsBodyHtml = False


            Try
                smtpClient.Send(eMail)
                Return True
            Catch ex As Exception

               Return False

            End Try
        End Function
    End Class

On sending mails outside my domain(gMail,Hotmail etc) I get : Mailbox unavailable. The server response was: Authentication is required for relay

However I have no trouble in sending emails on my own domain.

I have tried several changes but same error. Following does not work

  1. changing UseDefaultCredentials;
  2. enabling/disabling ssl ;

However when i used same SMTP settings in Outlook I got same error Server error: '550 Authentication is required for relay' When sending mails outside my own domain. such as on hotmail, gmail.

But when i changed accounts setting in outlook and ticked : My outgoing (SMTP) server requires authentication -> Use same settings as incoming mail server, I was able to send email to any domain.

I cant figure this out, can any one guide me?

Upvotes: 1

Views: 2055

Answers (2)

Uzair Khan
Uzair Khan

Reputation: 67

I figured it out somehow, but still cant explain why this is

Instead of declaring credentials in codebehind i declared mailsettings in webconfig

<system.net>
    <mailSettings>
      <smtp from="[email protected]">
        <network host="[email protected]" port="25" userName="[email protected]" password="secret" defaultCredentials="false" enableSsl="false" clientDomain="mydomain.com"/>
      </smtp>
    </mailSettings> 
  </system.net>

Then just used smtp client in code behind without setting credentials : 

Public Class sMail
    Public emailBody As String
    Public emailSubject As String
    Public sendTo As String

  Public Function sendMail() As Boolean
        Dim eMail As New System.Net.Mail.MailMessage
        eMail.Sender = New System.Net.Mail.MailAddress("[email protected]")
        eMail.Priority = Net.Mail.MailPriority.High
        eMail.From = New System.Net.Mail.MailAddress("[email protected]")
        eMail.To.Add(sendTo)
        eMail.Subject = emailSubject
        eMail.Body = emailBody
        eMail.IsBodyHtml = True
        eMail.BodyEncoding = Encoding.Default
        Dim smtpClient As New System.Net.Mail.SmtpClient()     
        Try
            smtpClient.Send(eMail)
            Return True
        Catch ex As Exception
           Return False
        End Try
  End Function
End Class

This method worked for me,It should also work with credentials declared in code behind instead of in web.config I guess, I am not sure, but didn't work for me

Upvotes: 0

joelmdev
joelmdev

Reputation: 11773

Ensure that the defaultCredentials attribute of the network element in your web.config isn't set to "true". See here for more details on how to configure mailSettings for use with System.Net.Mail.

Upvotes: 1

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