[vangale]

Along with this and Kong there is also https://github.com/mailhog/MailHog for testing SMTP failure scenarios on outgoing email.

[crdoconnor]

I wrote a similar thing to this too: https://github.com/hitchtest/hitchsmtp#bad-smtp-server

It just outputs the mail it receives to stdout as JSON for easy parsing. Sending to specific email addresses "e.g. [e-mail]" will trigger specific SMTP errors.