Added the following code to checkout.aspx.vb to check whether the customer has subscribed and if not email verification.
' If mailing list ticked, send email for verification
Dim tblCustomerData As New Data.DataTable
Dim numCustomerID as integer = objOrder.CustomerID
Dim sbdMailingText As StringBuilder = New StringBuilder()
Dim strMailingText As String
Dim ML_SendMail as boolean
If chkMailingList.Checked
tblCustomerData = objBasket.GetCustomerData(numCustomerID)
Dim strEmail As String = "", strPassword As String = ""
If tblCustomerData.Rows.Count > 0 Then
strEmail = FixNullFromDB(tblCustomerData.Rows(0).Item("U_EmailAddress")) & ""
ML_SendMail = FixNullFromDB(tblCustomerData.Rows(0).Item("U_ML_SendMail"))
End If
If not ML_SendMail then
objBasket.UpdateCustomerMailingList(strEmail, strPassword)
sbdMailingText.Append(GetGlobalResourceObject("Kartris", "EmailText_NewsletterSignup") & vbCrLf & vbCrLf)
sbdMailingText.Append("[WEBSHOPURL]Default.aspx?id=" & numCustomerID & "&r=" & strPassword & vbCrLf & vbCrLf)
sbdMailingText.Append(GetGlobalResourceObject("Kartris", "EmailText_NewsletterAuthorizeFooter"))
strMailingText = sbdMailingText.ToString
strMailingText = Replace(strMailingText, "[IPADDRESS]", Request.UserHostAddress())
strMailingText = Replace(strMailingText, "[WEBSHOPNAME]", GetGlobalResourceObject("Kartris", "Config_Webshopname"))
strMailingText = Replace(strMailingText, "[WEBSHOPURL]", WebShopURL)
strMailingText = strMailingText & GetGlobalResourceObject("Kartris", "ContentText_NewsletterSignup")
Dim strFrom As String = LanguagesBLL.GetEmailFrom(GetLanguageIDfromSession)
SendEmail(strFrom, strEmail, GetGlobalResourceObject("Kartris", "PageTitle_MailingList"), strMailingText)
End If
End if