ASP.net Emailing only works in debug mode

Hi
The following ASP.net VB.net code works in debug mode but does not work after I publish the site. Why might this be? Thanks

    Protected Sub btnContactMe_Click(sender As Object, e As EventArgs) Handles btnContactMe.Click

        Try
            Dim S As String = "Office2Web Enquiry "
            'NOTE OUNCTUATION MESSES WITH EMAILING
            S = S & "Name " & Me.txtName.Text & " Email " & Me.txtEmail.Text & " Contact Number " & Me.txtContactNumber.Text & " Company " & Me.txtCompany.Text
            S = S & " Description " & Me.TextBox1.Text
            Dim sEmailResult As String
            ''sEmailResult = oSendMailMessage("info@online-excel.com", "consulting@office2web.com.au", "murray@office2web.com.au", "", "Office2Web Enquiry", S, True)
            sEmailResult = oSendMailMessage("info@online-excel.com", "consulting@office2web.com.au", "murbro9@yahoo.com", "murray@office2web.com.au", "Office2Web Enquiry", S, True)

            If sEmailResult = "Email Success" Then
                Me.lblEmailResult.Text = "Message Sent. Thank you."
            Else
                Me.lblEmailResult.Text = "Sorry! Message not sent. " & sEmailResult
            End If
        Catch ex As Exception
            Me.lblEmailResult.Text = "Error message not sent " & ex.Message
        End Try

    End Sub

    Public Function oSendMailMessage(ByVal from As String, ByVal recepient As String, ByVal bcc As String,
                             ByVal cc As String, ByVal subject As String, ByVal body As String,
                             ByVal blnUseHTML As Boolean) As String
        Try

            ' Instantiate a new instance of MailMessage
            Dim mMailMessage As New MailMessage()

            ' Set the sender address of the mail message
            mMailMessage.From = New MailAddress(from)
            ' Set the recepient address of the mail message
            mMailMessage.To.Add(New MailAddress(recepient))

            ' Check if the bcc value is nothing or an empty string
            If Not bcc Is Nothing And bcc <> String.Empty Then
                ' Set the Bcc address of the mail message
                mMailMessage.Bcc.Add(New MailAddress(bcc))
            End If

            ' Check if the cc value is nothing or an empty value
            If Not cc Is Nothing And cc <> String.Empty Then
                ' Set the CC address of the mail message
                mMailMessage.CC.Add(New MailAddress(cc))
            End If

            ' Set the subject of the mail message
            mMailMessage.Subject = subject
            ' Set the body of the mail message
            mMailMessage.Body = body

            ' Set the format of the mail message body as HTML
            If blnUseHTML = True Then
                mMailMessage.IsBodyHtml = True
            Else
                mMailMessage.IsBodyHtml = False
            End If

            ' Set the priority of the mail message to normal
            mMailMessage.Priority = MailPriority.Normal

            ' Instantiate a new instance of SmtpClient
            Dim mSmtpClient As New SmtpClient()

            ' Send the mail message
            mSmtpClient.Send(mMailMessage)
            oSendMailMessage = "Email Success"

        Catch ex As Exception
            Dim oEX As String = ex.Message
            oSendMailMessage = "Email Not Sent! " & oEX
        End Try
    End Function