How to Send Emails in Flask using SMTP or Email API

A Flask email tutorial explains how to send messages through the Flask-Mail extension using SMTP or through Mailtrap’s API client. It covers installing Flask and Flask-Mail, optionally creating isolated virtual environments, configuring SMTP credentials, and creating Message objects for plain-text or HTML emails. The tutorial also demonstrates sending to multiple recipients with CC, BCC, reply-to fields, attachments, and embedded images, while recommending appropriate MIME types and both HTML and text alternatives. For nonblocking delivery, it presents threading and Celery with Redis, including the need for a separate Celery worker, and shows how to reuse SMTP connections or Mailtrap’s Bulk Stream for high-volume messages. It further describes API-based sending with authentication tokens, attachments encoded in Base64, bulk API requests, and asynchronous API delivery. Production guidance includes disabling Flask debug mode, avoiding hardcoded credentials by using environment variables, and verifying sender domains.

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