One neat feature of Outlook is that you can avoid memorizing long, confusing e-mail addresses of people to whom you send mail frequently. If the intended recipient is entered in your Contacts list and you've included an e-mail address in the Contact record, all you have to type in the To box of your e-mail form is the person's name — or even just a part of the person's name. Outlook helps you fill in the rest of the person's name and figures out the e-mail address. You know that you've got it right when Outlook underlines the name with a solid black line after you press the Tab key or click outside the To box.

If Outlook underlines the name with a red wavy line, Outlook thinks that it knows the name you're entering, but the name isn't spelled quite right, so you need to correct the spelling.

If Outlook underlines the name with a dotted green line, Outlook has more than one possible match to the name you're entering. Right-click the name and choose the correct person from a list of suggestions.

If Outlook doesn't put any underline below the name, it's telling you that it has no idea to whom you're sending the message but that it will use the name that you typed as the literal e-mail address. So you have to be doubly sure that the name is correct.