NodeMailer is a module for Node.js applications to allow easy email sending. From the same authors also comes NodemailerApp, an application created to help you debug email.
NodemailerApp includes local SMTP and POP3 servers, a sendmail replacement, catchall email domain service, AMP4Email renderer […] You can use NodemailerApp to instantly preview emails sent from your dev environment, be it from SMTP or sendmail or even from the open web via built-in catchall service. You can also upload any email to an external SMTP or IMAP server. All SMTP, POP3 and IMAP transactions include live logs for extra clarity.
And no, you don’t need to use Node or Nodemailer to use NodemailerApp