A person wants to exchange emails, we walk over to a computer, I open my Yahoo mail account, I start to compose an email. I then ask them to type in their email so there are no mistakes, after they do so, I compose a letter or email something like this,
Subject: Andy from Seoul Backpackers Hostel (or -- Their name, people need good subject lines or they just delete, their name is the only thing they know well.)
This is Andy we met in the Seoul Backpackers; please respond so I know this email works correctly.
Too funny for words, only about 1 in 10 ever reply, so in a way there is little reason to exchange emails, I do so because the people who reply are genuinely good people, and sometimes what I thought was a good person and my friend is really a self-center lout.
The better friends are one who feels an obligation to reply to emails as good manners.