无法连接到 SMTP 主机：smtp.gmail.com，端口：android 中的 587

问：

提供了如此多的跟踪以通过邮件发送附件，但收到此错误“javax.mail.MessagingException：无法连接到 SMTP 主机：smtp.gmail.com，端口：587; 嵌套异常为：java.net.NoRouteToHostException：主机无法访问”

不明白出了什么问题，请找到以下编码详细信息

单击按钮，调用 JavaMailAPI 并将邮件详细信息 f=of 两个发送方传递给接收方

Java邮件API.java

    public class JavaMailAPI extends javax.mail.Authenticator {
    private String mailhost = "smtp.gmail.com";
    private String user;
    private String password;
    private Session session;
    private Multipart _multipart = new MimeMultipart();
    static {
        Security.addProvider(new com.example.sendmail.JSSEProvider());
    }
    public JavaMailAPI(String user, String password) {
        this.user = user;
        this.password = password;
        Properties props = new Properties();
        props.setProperty("mail.transport.protocol", "smtp");
        props.setProperty("mail.host", mailhost);
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.socketFactory.port", "587");
        props.put("mail.smtp.socketFactory.class",
                "javax.net.ssl.SSLSocketFactory");
        props.put("mail.smtp.socketFactory.fallback", "false");
        props.setProperty("mail.smtp.quitwait", "false");
        session = Session.getDefaultInstance(props, this);
    }
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(user, password);
    }
    public synchronized void sendMail(String subject, String body,
                                      String sender, String recipients) throws Exception {
        try {
            MimeMessage message = new MimeMessage(session);
            DataHandler handler = new DataHandler(new ByteArrayDataSource(
                    body.getBytes(), "text/plain"));
            message.setSender(new InternetAddress(sender));
            message.setSubject(subject);
            message.setDataHandler(handler);
            BodyPart messageBodyPart = new MimeBodyPart();
            messageBodyPart.setText(body);
            _multipart.addBodyPart(messageBodyPart);
            // Put parts in message
            message.setContent(_multipart);
            if (recipients.indexOf(',') > 0)
                message.setRecipients(Message.RecipientType.TO,
                        InternetAddress.parse(recipients));
            else
                message.setRecipient(Message.RecipientType.TO,
                        new InternetAddress(recipients));
            Transport.send(message);
        } catch (Exception e) {
        e.printStackTrace();
        }
    }
    public void addAttachment(String filename) throws Exception {
        BodyPart messageBodyPart = new MimeBodyPart();
        DataSource source = new FileDataSource(filename);
        messageBodyPart.setDataHandler(new DataHandler(source));
        messageBodyPart.setFileName("download image");
        _multipart.addBodyPart(messageBodyPart);
    }
    public class ByteArrayDataSource implements DataSource {
        private byte[] data;
        private String type;
        public ByteArrayDataSource(byte[] data, String type) {
            super();
            this.data = data;
            this.type = type;
        }
        public ByteArrayDataSource(byte[] data) {
            super();
            this.data = data;
        }
        public void setType(String type) {
            this.type = type;
        }
        public String getContentType() {
            if (type == null)
                return "application/octet-stream";
            else
                return type;
        }
        public InputStream getInputStream() throws IOException {
            return new ByteArrayInputStream(data);
        }
        public String getName() {
            return "ByteArrayDataSource";
        }
        public OutputStream getOutputStream() throws IOException {
            throw new IOException("Not Supported");
        }
    }
    }

JSSE编译器.java

 public final class JSSEProvider extends Provider {
    public JSSEProvider() {
        super("HarmonyJSSE", 1.0, "Harmony JSSE Provider");
        AccessController
                .doPrivileged(new java.security.PrivilegedAction<Void>() {
                    public Void run() {
                        put("SSLContext.TLS",
                                "org.apache.harmony.xnet.provider.jsse.SSLContextImpl");
                        put("Alg.Alias.SSLContext.TLSv1", "TLS");
                        put("KeyManagerFactory.X509",
                            

"org.apache.harmony.xnet.provider.jsse.KeyManagerFactoryImpl");
                        put("TrustManagerFactory.X509",
                                "org.apache.harmony.xnet.provider.jsse.TrustManagerFactoryImpl");
                        return null;
                    }
                });
    }
    }

在gradle中添加了以下jar

implementation files('libs/activation.jar')
implementation files('libs/additionnal.jar')
implementation files('libs/mail.jar')

并在清单中添加了 Internet 权限

不明白出了什么问题，请帮我解决它。谢谢