Have you ever tried to create a closed or private site for your coworkers, friends or students? The problem is that if your membership policy does not state "Open" you have 3 options:
invite your users one by one to the new site (e.g. by email),
set up a password they can use when joining (password-protected membership),
or let them apply for membership and accept each application individually.
It's not that bad, but we can make it easier. What if your organisation uses a single domain for emails? Burch Kealeysuggested that it would be much easier if he could whitelist a domain in a way that every Wikidot user with an email from whitelisted domains can do a 1-click join.
Here how it's done:
1. Go to your Site Manager and enter whitelisted domains (wildcards work too!)
It's available in Site Manager in Security » Access Policy
2. Put a Join module on your site if it's not there already
3. Wikidot users from matching domains will be able to join your site instantly
Domain whitelisting is available for Pro+ and educational wikis. I hope you can find a good use for it!