Send Text, HTML, and Attachment Emails with Spring Boot

Add the Spring Boot mail starter and configure the provider's SMTP host, port, authentication, and TLS mode. Store credentials in environment variables or a secret manager.

Plain text:

SimpleMailMessage message = new SimpleMailMessage();
message.setTo("receiver@example.com");
message.setSubject("Hello");
message.setText("Plain-text message");
mailSender.send(message);

HTML and attachments:

MimeMessage mime = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(mime, true, "UTF-8");
helper.setTo("receiver@example.com");
helper.setSubject("Report");
helper.setText("<h1>Report</h1>", true);
helper.addAttachment("report.pdf", new File("/safe/path/report.pdf"));
mailSender.send(mime);

Do not insert untrusted HTML without sanitization. Validate attachment paths and sizes, set connection and write timeouts, log provider response identifiers rather than message contents, and use asynchronous delivery or a queue when email should not delay an HTTP request.