Recently, I needed to find out everything — everything — everything about the domains of one organization, and I knew only one domain name that she owns.
In the process of solving the problem, I came across a wonderful web service -
whois-search.ru , although it can only search using the RIPN database, but in most cases it is enough.

I will show all the greatness of this service on the example of Habr.
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1. We write in the search box habrahabr.ru
2. Get information on the domain, and click on the contents of the field "organization" - Invento Holdings Limited
3. We receive information on all domains of the organization.
Mine is not bad.
What is convenient - the fact that the search can be carried out on almost any field and use wildcard symbols, so you can dig up a lot of interesting things.