Sounds complicated, but only takes a few seconds.
Once you've viewed the e-mail address, close the Contact form and choose Don't Save (unless you really want to create a contact for that sender, in which case, hit Save). The icon all the way on the right (picture of an index card) will open an Outlook Contact form, where the full e-mail address of the Sender will be displayed. However, if you hover over the From address, a pop-up window will appear, with a number of icons along the bottom.
The same can happen if you hit Reply (with the intention of deleting the Reply e-mail before sending it). Seeing the full e-mail address of the sender is a little more complicated, because hovering over the From alias usually displays only a truncated portion of the actual e-mail address. A pop-up will expand to show the actual e-mail address tied to that alias. To see which e-mail address an e-mail was sent to, open the specific e-mail, then hover over the alias in the e-mail header's To field. It will usually bring up a contextual menu that shows choices of actions available for the element that is selected at the time. This post describes to steps to setup the Auto Response Email for MAC Mail or Microsoft Outlook email client with IMAP, POP or any other personal Email account. On any Mac, holding down the Control key and clicking is the equivalent of right-clicking on a PC.