For instance, you may search any old correspondence with that person in your mail archives, use a people search engine (like Pipl), use the WHOIS data of that person’s website or, if nothing works, search for that person’s name on Google (include the @ symbol in quotes) and you may sometimes find their email address in the search results.
Related Tutorial: How to Verify an Email Address
How to Find Someone’s Email Address
There’s however a better way. You can guess a few addresses and then use LinkedIn’s Rapportive add-on for Gmail to verify if any of your guesses point to the right person or not.
Go to your Gmail inbox, compose a new message and enter the email address that you have guessed. Now hover your mouse over the address and Rapportive will show a list of various social profiles – Facebook, Twitter and LinkedIn – that are associated with the email address.
If you are to recognize a profile in the social results, you can be pretty much sure that your guess was correct. If no social results are found for that email address, it means either that email address doesn’t exist, or the person doesn’t have a social presence or they could have associated a different email address with their social profiles.
Rapportive is available for Chrome, Firefox and Safari and you’ve to have a Gmail account to use this tool.