Answer 1

Nodemailer is a library.
You need a proper SMTP mail server.

Answer 2

Nodemailer is a library that helps you send message to a SMTP mail server. Think of it as the SMS app on your phone. Its free, unlimited use.

SMTP mailserver is something like your phone network provider, such as AT&T.

Without the SMTP mailserver, your mails are not getting sent out.

Similarly without phone network provider, your SMS are not getting sent out.

Nevertheless, you can spam your outbox.