Giving everyone except external users access without sending an email notification

Hi u156531 - 

1. Go to List Settings
2. Permissions for this List
3. If the List is inheriting from the parent (the Site)
   1. Click 'Stop inheriting Permissions' if you don't want to grant this group access at the Site level
   2. Click 'Manage Parent' to add the group of folks at the Site level, and thus also to the List
4. In the ribbon, click 'Grant Permissions'
5. Type in the name(s)
6. Uncheck the box to send an email
7. Select Edit or Contribute from the drop down
8. Click Share

Hope that helps!