How to Send Email in Java using Gmail SMTP and Gmail API

A comprehensive Java email tutorial explains how to send messages through Gmail using either SMTP with Jakarta Mail or the Gmail API with OAuth 2.0. The SMTP approach involves configuring Maven dependencies, using Gmail’s SSL port 465 or TLS port 587, authenticating with two-step verification and an app password, and creating MIME messages for plain text, HTML, embedded images, and file attachments. It notes Gmail SMTP restrictions including daily sending volumes, a 25 MB attachment limit, recipient limits, and required secure connections. The Gmail API method requires creating a Google Cloud project, enabling the API, configuring OAuth credentials, installing client libraries, authorizing a user, and base64url-encoding MIME messages before creating drafts or sending them through the API. API use offers broader Gmail functionality and OAuth-based security but involves quotas, rate limits, concurrent-request restrictions, and similar size and sending constraints. The comparison presents SMTP as simpler for basic sending and the API as more flexible for deeper Gmail integration, while suggesting dedicated email services such as Mailtrap as alternatives for high-volume delivery, analytics, and SMTP or API-based integration.

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