A whois directory is a database that stores information about domain names and their owners. While whois directories can be useful for finding contact information for website owners, they have several limitations:-

First, whois directories only contain publicly available information. This means that if a domain owner has chosen to keep their contact information private, it will not be listed in a whois directory

Second, whois directories can be out of date. If a domain owner changes their contact information, the new details may not be immediately reflected in the whois directory. This can make it difficult to get in touch with the correct person.

Finally, whois directories only contain basic contact information. They do not usually include other important details such as website content or server location. This makes them less useful for people trying to troubleshoot website problems or track down malicious activity.

Conclusion:

Despite of all these Limitations I would still insist you guys to Try Promoting your service/ Products via this whois database service. But why ?
Well Hundreds and thousands of companies are following this approach and expanding their business.. They have found the way to reach their ROIs. It Might take some time to get the ROI since this you have to bear tool cost and then email marketing or cold calling cost in the initial phase; But thereafter the Profitability would give you atleast 3-4X return as told by our esteemed customers.