Using your SMTP (HigLabo.Mail.dll ver 18.104.22.168), I have a problem with Read receipts, the sender doesn't receive this mail. I use these code lines for to send the request:
mailMsg = New HigLabo.Net.Smtp.SmtpMessage
mailMsg.Headers.Add(New HigLabo.Net.Smtp.SmtpMailHeader("Return-Receipt-To", "email@example.com")) For
information I'm sure that server manage this request, because using standard .NET Framework
library (System.Net.Mail) with the property DeliveryNotificationOptions=DeliveryNotificationOptions.OnSuccess, it works, while if use header "Return-Receipt-To" also this don't works.
Can you help me please ?