JavaMail API – Gmail SMTP経由でメールを送信する例
この記事では、Gmail SMTPサーバー経由でメールを送信する方法を示します。
Javaでメールを送信するには、JavaMailが必要です
pom.xml
com.sun.mail javax.mail 1.6.2
1. TLS経由のGmail SMTP
SMTP = smtp.gmail.com Port = 587
SendEmailTLS.java
package com.example;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Properties;
public class SendEmailTLS {
public static void main(String[] args) {
final String username = "[email protected]";
final String password = "password";
Properties prop = new Properties();
prop.put("mail.smtp.host", "smtp.gmail.com");
prop.put("mail.smtp.port", "587");
prop.put("mail.smtp.auth", "true");
prop.put("mail.smtp.starttls.enable", "true"); //TLS
Session session = Session.getInstance(prop,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}
});
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("[email protected]"));
message.setRecipients(
Message.RecipientType.TO,
InternetAddress.parse("[email protected], [email protected]")
);
message.setSubject("Testing Gmail TLS");
message.setText("Dear Mail Crawler,"
+ "\n\n Please do not spam my email!");
Transport.send(message);
System.out.println("Done");
} catch (MessagingException e) {
e.printStackTrace();
}
}
}
2. SSL経由のGmail
2.1 The logic is the same, just pass in different properties values.
SMTP = smtp.gmail.com Port = 465
SendEmailSSL.java
package com.example;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Properties;
public class SendEmailSSL {
public static void main(String[] args) {
final String username = "[email protected]";
final String password = "password";
Properties prop = new Properties();
prop.put("mail.smtp.host", "smtp.gmail.com");
prop.put("mail.smtp.port", "465");
prop.put("mail.smtp.auth", "true");
prop.put("mail.smtp.socketFactory.port", "465");
prop.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
Session session = Session.getInstance(prop,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}
});
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("[email protected]"));
message.setRecipients(
Message.RecipientType.TO,
InternetAddress.parse("[email protected], [email protected]")
);
message.setSubject("Testing Gmail SSL");
message.setText("Dear Mail Crawler,"
+ "\n\n Please do not spam my email!");
Transport.send(message);
System.out.println("Done");
} catch (MessagingException e) {
e.printStackTrace();
}
}
}
3. アプリケーション固有のパスワードが必要です
3.1 If 2-Step verification is ON. 次のエラーメッセージが表示されます。
Caused by: javax.mail.AuthenticationFailedException: 534-5.7.9 Application-specific password required. Learn more at
534 5.7.9 https://support.google.com/mail/?p=InvalidSecondFactor - gsmtp
at com.sun.mail.smtp.SMTPTransport$Authenticator.authenticate(SMTPTransport.java:965)
at com.sun.mail.smtp.SMTPTransport.authenticate(SMTPTransport.java:876)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:780)
at javax.mail.Service.connect(Service.java:388)
at javax.mail.Service.connect(Service.java:246)
at javax.mail.Service.connect(Service.java:195)
at javax.mail.Transport.send0(Transport.java:254)
at javax.mail.Transport.send(Transport.java:124)
at com.example.calculator.SendEmail.main(SendEmail.java:41)
3.2 To fix it, follow this guide to create an App Password
コードに違いはありません。代わりに、新しく生成されたアプリのパスワードを入力するだけです。
SendEmail.java
package com.example;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Properties;
public class SendEmail {
public static void main(String[] args) {
final String username = "[email protected]";
final String password = "puts your app password here"; // update here
// same code...
}
}
java.net.UnknownHostException: smtp.gmail.com
ファイアウォールまたはプロキシサーバーがこのsmtp.gmail.comをブロックしていないことを確認してください