* [Inbucket v3.2.0](https://github.com/inbucket/inbucket) – Disposable webmail server providing built-in SMTP, POP3, REST and web interfaces without requiring a database.

* [MailTime 5.3.0](https://github.com/veliovgroup/mail-time) – Email queuing system that extends Nodemailer with multi-SMTP rotation, storage-backed retries, and horizontal scaling support.

* [smtp-server v3.19.19](https://github.com/nodemailer/smtp-server) – Node.js module for creating SMTP and LMTP server instances dynamically.

* [Maddy Mail Server v0.9.6](https://github.com/foxcpp/maddy) – Composable all-in-one mail server implementing SMTP (MTA/MX), IMAP storage, and security protocols such as DKIM, SPF, DMARC, and DANE.