When composing an email, entering a character into the "To" or "Cc" lines will trigger Mail to provide a list of all contacts matching that entry (typically, for one character entry, any First Name, Last Name or email address beginning with the character are listed in popup form).  Unfortunately, the search appears to be done on ALL contacts in the Contacts app., starting at the Personal folder level. 

I have a long list of former work contacts, contained in a folder under Personal/General/Old Work.  I no longer have common reasons to email them, and would prefer that those names not clutter up the popup list of names in the To or Cc fields.  Short of deleting these Old Work contacts completely (which I do not want to do), is there any sort of work around to create a folder/subfolder set that would not be searched by the popup helper?  Or some method of organizing contacts that I have not thought of?