TeamTools gets users from your Google Apps Directory. To see your Directory, go to Contacts and click on the Directory link in the left column.
Suspended and deleted users are not shown either under the Directory section or in TeamTools. In addition, your Google Apps administrator can disable Contact Sharing for certain users, which will cause them to not appear.
Note that if your Google Apps administrator has chosen to do so, you might also see “domain shared contacts” in your Directory. These are people who don’t have email addresses in your domain, but who you need to be able to contact. These contacts do not appear in TeamTools.