Why not just conduct a check on the person via the internet. There are many companies out there that will search and find the person for a small fee. You can then mail them a certified letter. If you want to send it via email, just send it return receipt requested. Most email platforms have this option in their settings. One thing about a libel or slander action, they are difficult to win, sometimes hard to establish damage and courts do not like them crowding up their calendars.
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Also if the online publication is corporation or Limited Liability Company, then you can perform a search on the California Secretary of State Business entity locator. That will usually provide you with either the address of the company, or the agent for service of process. Both of those would be acceptable to send the notice to. You also could search for dba filings, although those are more difficult and you need to know the county where that would be filed.
The answer is actually much simpler than prior responses. Every website is registered with an address and email. Some use a proxy. In those cases, any letter you send will be forwarded to them by the proxy. If the website it who you are trying to contact you only need go to www.whois.com and type in the website. It will let you know which ones are available to buy. Scroll down and click on 'whois' next to the website in question and whalla! you have your owner. If it is a proxy, you send the letter to them and they will get it. They have legally designated the proxy as their agent and service on the proxy is considered proper service of process. If you want proof, send the letter registered mail, return receipt requested. You can also email it.
The recommendations in this answer are not considered legal advice for the purposes of ethical evaluation, nor do the create a retention of counsel wherein an attorney-client relationship exists. These recommendations should never be relied upon without first consulting an attorney in your jurisdiction. I am not your attorney, unless we enter into a written agreement fulfilling the terms of that agreement. The comments posted herein are purely for educational purposes and public discourse only.
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