How to Send Emails with Spring Boot in Minutes: A Step‑by‑Step Guide
This guide explains the fundamentals of email protocols, shows how to configure Spring Boot’s mail starter, and provides complete code examples for sending plain‑text and HTML emails—including dependency setup, property configuration, and unit‑test snippets—so developers can quickly integrate reliable email functionality into their Java backend applications.
Email Protocol Overview
SMTP
Simple Mail Transfer Protocol (SMTP) is the standard protocol for transmitting email between servers. It uses TCP port 25 and supports authentication to reduce spam.
POP3
Post Office Protocol version 3 (POP3) retrieves email from a server, typically deleting the messages after download. It operates on TCP port 110.
IMAP
Internet Message Access Protocol (IMAP) improves on POP3 by allowing selective download of messages and server‑side folder management. It uses TCP port 143.
Spring Boot Mail Integration
Dependency
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-mail</artifactId>
</dependency>Configuration
Add the following properties to application.properties. Adjust the host, username, and password for your email provider.
spring.mail.host=smtp.qq.com
[email protected]
spring.mail.password=123456
spring.mail.default-encoding=UTF-8For other providers replace the host, e.g., smtp.163.com for 163.com.
Enabling IMAP/SMTP for QQ Mail
Log into QQ Mail, go to Settings → Account → POP3/IMAP/SMTP/Exchange/CardDAV/CalDAV services, enable the IMAP/SMTP service, and copy the displayed authorization code. Use this code as spring.mail.password.
Sending Plain‑Text Email
Inject JavaMailSender and use SimpleMailMessage to send a basic email.
@RunWith(SpringRunner.class)
@SpringBootTest
public class MailTests {
@Resource
private JavaMailSender javaMailSender;
@Test
public void sendMail() {
SimpleMailMessage msg = new SimpleMailMessage();
msg.setFrom("[email protected]");
msg.setTo("[email protected]");
msg.setSubject("程序新视界");
msg.setText("技术分享");
// Optional CC:
// msg.setCc("[email protected]", "[email protected]");
javaMailSender.send(msg);
}
}Sending HTML Email
Use MimeMessage with MimeMessageHelper for rich‑text content, attachments, or inline resources.
@Test
public void sendHtmlMail() {
String content = "<html>
" +
"<body>
" +
" <h3>hello world ! 这是一封html邮件!</h3>
" +
"</body>
" +
"</html>";
MimeMessage message = javaMailSender.createMimeMessage();
try {
MimeMessageHelper helper = new MimeMessageHelper(message, true);
helper.setFrom("[email protected]");
helper.setTo("[email protected]");
helper.setSubject("程序新视界");
helper.setText(content, true);
// Example attachment:
// helper.addAttachment("file.txt", new File("path/to/file"));
javaMailSender.send(message);
} catch (MessagingException e) {
System.out.println("发送邮件异常");
}
}Additional Considerations
In production environments you may need email templates, external email service APIs, comprehensive error handling, delivery monitoring, and attachment management.
Source code repository: https://github.com/secbr/springboot-learn/tree/master/springboot-mail
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