In that case, yes. Open the contact. Hit the down arrow just to the left of the e-mail address and select "E-mail 2". Then type in the second e-mail address. Save and close.
Now for an example of how to use this:
Let's say you have a contact named testing. E-mail address is test@somewhere.com, E-mail 2 is test@somewhereelse.net. If you want to send a particular e-mail to both these accounts at the same time, create a new message to: testing,testing - you'll see a red squiggly line (technical term) beneath both of these. Type your message and hit send. A new window will open saying that Outlook found more than 1 match and asking which address to you mean for [the first] testing - choose test@somewhere.com and click OK. Then you will immediately see the same dialog again asking who the second testing is - choose test@somewhereelse.net. When you click OK for this one, your mail will be sent to both addresses.
Obviously, if you only want to send to 1 at a time, just enter 1 testing in the To: field and you will only be asked once which address you're sending to.
