NodemailerApp is the ultimate cross platform email debugging app.
App includes local SMTP and POP3 servers, a sendmail replacement, and it imports emails from EML files, EMLX files, large MBOX files from Gmail takeout, Maildir folders and Postfix queue files for inspection and preview. Ever wanted to view the actual HTML source of a nicely designed email instead of some garbled rfc822 text? Just open the HTML tab of an email to see it.
Preview emails either in rich text or plain text mode. View the source of the entire message or the decoded HTML content
Sendmail replacement to catch emails from applications that pipe to sendmail (eg. PHP mail(…)).
Local development server to catch emails from applications that send via SMTP (Nodemailer, PHPMailer etc.).
Message upload to relay a caught message either to next SMTP server or to an IMAP server.
Extensive search to find long lost emails.
Large mailbox import. Received a 10GB mbox takeout file from Gmail? No problem, just import it to NodemailerApp.
Catchall service to accept messages from the internet.