Cannot Enter email address without an address book list popping up

GW 8.0.2. I have one user that cannot type an email address into the to: field without a list of addresses popping up for him to choose from. Example: He enters All email addresses that begin with sales in the GW address book appear for him to make a selection and will not let him use the email address as typed. It adds the email address to the list if he puts it in a personal addressbook or in frequent contacts. I have run a GWCheck structure and contents against his database. Not sure where else to look.