Question about Outlook Express

I am having a hard time explaining this, but when I am trying to compose a message, I would type the first few letters of a person's name and outlook would autocomplete it. That's not happening anymore and I can't figure out why. 

Any help is appreciated. 

For example, I used to want to send an email to Joe Alstat and in the "To" field I would start typing "Joe" and it would autocomplete for me the rest of the name. 

Thanks for your help.