Use cases
Pick the situation closest to yours. Each route links directly to the message API, configuration, security settings, and optional modules involved.
01 · Message structure
Declare plain text, HTML, inline images, attachments, or calendar events and Simple Java Mail builds the MIME tree mail clients expect. Your code does not have to assemble multipart nesting, content IDs, transfer encoding, and transport plumbing by hand.
02 · Security
Protect the SMTP connection with TLS, use a password or refresh-aware OAuth2 token, sign the sending domain with DKIM, or sign and encrypt message content with S/MIME. These are separate layers, so you can apply the ones your mail flow needs.
03 · Sustained load
When several workers send continuously, use bounded worker threads and reuse physical SMTP connections in a pool. Cluster keys can keep workloads separate or spread one workload over several SMTP servers.
04 · Known workloads
For a known list or a caller-owned queue, keep one SMTP connection open and send sequentially. This is part of the core API. Move to pooled delivery only when you need concurrency or sustained throughput.
05 · Application fit
Configure a mailer in Java, properties, environment variables, or Spring. You can also supply your own Jakarta Mail Session, work through an authenticated SOCKS proxy, or send and test from the command line.
06 · Troubleshooting
Test the exact mailer configuration without sending a message, inspect the effective settings, route Jakarta Mail's protocol output into your logs, and read the SMTP server's submission replies.
