Background: We have observed a situation in which we forward email to someone, and cc lib-instruct; then, when we receive the email by virtue of being on the lib-instruct listserv, we don't see the recipient's email address anywhere on the email. So we automatically think the recipient did not receive it, but they did (which we checked by looking at Sent Items).
Here is what Bob Crovo told me regarding the Case of the Disappearing E-mail Address:
"It's an annoying thing about how Outlook handles email. If you look at the email in the menu before you open it, you can right-click the item and choose Message Options. This shows you the headers in another window. You can scroll through and find all the To: lines and you'll see that the info was included in the headers. Outlook doesn't display them to you."
Try it, it works! This is somewhat convoluted, and difficult to explain. Please post a comment if you have questions.