If you send a different email for every recipient, you get a message ID which you can see in the headers. When mail bounces, you get the recipient _and_ your m

If you send a different email for every recipient, you get a message ID which you can see in the headers. When mail bounces, you get the recipient _and_ your message ID which made the mail bounce. Usually this bounce emails are discarded; but in this case you need them to take into account non-deliverable adresses: this is your first metric (delivered ;-). For opening: tracking pixels are your answer here. Opening attachments: not usually tracked. PDFs (for example) can either load tracking pixels or run javascript. Clic-thru: Tracking URLs with redirections.