I use Whois privacy on some of my domain names for competitive reasons. I don’t necessarily want people to know I own or acquired certain domain names, and having privacy enabled is an inexpensive way to keep some registrations private.
Just because I have privacy enabled on domain names, it does not necessarily mean that I am not interested in selling domain names. Although I have found that the majority of people contact me using links on the landing page of these domain names, I am fairly regularly contacted via email found during a Whois lookup.
One issue I have found is that some privacy services do not forward emails to the registrant. I believe sometimes this is intentional, and I think other times it’s unintentional. I suppose there are many people who use privacy protection to reduce or eliminate spam, and obviously if privacy emails are forwarded, that would become annoying. In my case, however, I don’t usually mind the emails, but I simply want to prevent others from knowing what I am buying.
I don’t have a list of registrars whose privacy services do or do not forward emails, and I don’t really think it would be possible to obtain a list like this. The best advice would be to test the proxy email address to see if your email is forwarded to you. If it doesn’t make it, contact the registrar to inquire about why. Perhaps this is related to some sort of error, or perhaps the privacy service simply does not forward emails (or has an alternative way for emails to be sent to registrants).
If someone is trying to get in touch with me about a domain name, I want them to be able to do so easily. Sending an email to the Whois registrant is a common way for someone to get in touch with a domain owner, but if it doesn’t work, important emails may be lost.