Nodemailer Email Library

Nodemailer is the most widely used email-sending module for Node-dot-js applications, created by Andris Reinman in 2010. The library enables developers to send emails through SMTP servers or direct delivery, supporting plain text, HTML, attachments, embedded images, calendars, and alternative content types within a single message. Nodemailer handles complex email construction through a simple JavaScript object API where developers specify sender, recipients, subject, body, attachments, and headers, with the library managing MIME encoding, content transfer encoding, boundary generation, and character set conversion automatically. The transport system supports multiple delivery methods including SMTP with TLS and STARTTLS encryption, Amazon SES through the built-in transport, sendmail for local mail agents, and stream transport for testing. The SMTP transport includes connection pooling for performance, OAuth2 authentication for Gmail and Microsoft accounts, DNS-based delivery routing, and automatic retry logic for transient failures. The attachment system supports files from disk paths, streams, buffers, and URLs, with content type detection, filename encoding for international characters, and content ID assignment for inline images referenced in HTML through cid URLs.