I think your requirement is mainly oriented around giving the users visibility to what emails have been sent. The sent items folder would be one method to allow this to occur. In the past, I’ve solved this problem by adding a BCC Address that would literally send the email directly to either a distribution list, user, or shared mailbox that allowed the users to review what had been sent.
Try this with an outlook rule of some kind to move the item to their sent items folder marked as read.
using (var mailMessage = new MailMessage(
var smtpClient = new SmtpClient("SmtpHost")
EnableSsl = false,
DeliveryMethod = SmtpDeliveryMethod.Network
// Apply credentials
smtpClient.Credentials = new NetworkCredential("smtpUsername", "smtpPassword");
Thanks & Regards