How can we improve WHMCS?

When a user goes to "Create a New Quote", there is an option to choose "Quote an Existing Client".

If you type in a letter of the alphabet, such as "A", you will see a complete listing of customers that start with "A", and you will also see their email addresses.

Is it possible from preventing users from seeing the dropdown full of email addresses? I am uncomfortable with staff being able to get a full list of names and email addresses.