How to Send HTML Emails in Python using SMTP and email API

Python developers can send HTML emails using the standard `smtplib` module for SMTP connections and the `email` MIME libraries to construct structured messages with HTML, plain-text fallbacks, headers, attachments, and embedded content. The guide demonstrates connecting to Mailtrap’s SMTP server, authenticating with valid credentials, creating multipart alternative messages so clients can fall back to plain text if HTML fails, and sending messages through `sendmail`. It also explains sending to multiple recipients with To, CC, and BCC fields, using CSV data to personalize bulk emails, and attaching files by encoding binary content with Base64 and MIME headers. Images can be included through CID attachments, Base64 data URLs, or externally hosted links, each with tradeoffs involving compatibility, file size, privacy, and client-side image blocking. Mailtrap-specific limits include a 10 MB total email size by default and 2 MB template-image uploads, while recommended practices include compressing images, using common file formats, scanning attachments for malware, securing credentials with environment variables, and monitoring delivery or API usage. As an alternative to SMTP, the Mailtrap Python SDK offers API-based sending with simpler configuration, template support, attachments, CC/BCC options, and scalability for high-volume email workloads.

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