Providing permission for creating / editing / deleting / reading your wiki pages to all your company/organization's users. Persons having same email domain in your company/organization can access your wiki i.e., whoever has "@yourcompany.com" email address.
How to set 'domain level' permission?
Go to Settings, Click Permissions
Select Domain in Reading combo box.
Save the settings.
Under Company/Organization Domain, enter your email domain and click Save
Screencast Demo for setting Domain Level Permission