On Fri, Jan 06, 2012 at 10:59:25PM -0500, Shawn H Corey wrote: > If my machine marks it as read This is local to your machine and may or may not be implemented by your mail user agent (MUA). Most MUA's implement it, actually. > and sends back a receipt saying so, the This is not part of the SMTP protocol. Not every MUA will do this. This is actually a feature added by Outlook/Exchange, and other MUAs don't do this at all. I guess you're a Windows user and you don't use Linux hardly at all, then, if you're not aware that this isn't done on Linux machines (anyone know about whether Mac native MUA's do this?). Well, maybe Thunderbird or similar MUAs have some kind of Outlook/Exchange compatibility code that can read these things. When I was using it (at a company that used Exchange) it would ask me if I wanted to acknowledge receipt, and I always said no. I don't know if it ack'ed behind my back, or what. No one at the company complained to me that I wasn't reading their emails. Derek's point about the mail logs is true, but in my case I run a mail server at home, and I have a smarthost that relays mail for me to the ultimate destination. My mail logs only confirm delivery to my smarthost. I have to get my ISP's cooperation to look at their mail logs (and mostly that goes along the lines of "we'll look at the logs for you" - as it probably should be - they shouldn't be letting me look at all their other customer's mail logs along with mine (they are mingled in one log)). I did actually do that once when mails to a friend were getting rejected (I did receive the bounce messages). Eventually I made a special route for her that goes straight from my machine to her mail server, her mail server accepted those. In general, there might be a few mail servers between you and the ultimate recipient, and you would need to look at the last one to tell if the letter had been delivered to where the recipient would be able to read it. bjb