How do people get on my Gmail contact list?

Sometimes I email people once or twice on Gmail. Maybe a day or so later, Gmail automatically adds the email contact (if it is also a gmail email) on my Gmail chat buddy list and I can see if he/she is online, and we somehow end up talking (or ignoring each other). This happens with a lot of my contacts, including people who I don't even care to talk to, like some lady I did a Craigslist sale with. Gmail also has the option of manually adding contacts.





I'm asking because I want to add this contact whom I have a crush on. We've emailed once or twice, but unlike other gmail contacts, this person has not been automatically added on to my list. I don't want to manually add him. I want him to think it was an "accident" that he got on my contact list.
How do people get on my Gmail contact list?
Well, you are right with your observation that Gmail automatically adds contacts in your list if you frequently email them. But when some people don't appear in your list, they might have some privacy settings in their end. Sorry about my answer, but that is really what i think.





If you want, you double check your list of contacts.


https://mail.google.com/mail/?zx=1kmthvw...





I would assume this should also direct you to the same page.