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JavaxException Unknown SMTP host Exception: mail.gmail.com

I am trying to send mail using Java code . The code is working fine when running on my personal PC . But on office network the exception of unknown SMTP host is appearing. Also my office pc is not able to ping smtp.gmail.com. PC firewall is closed as well.
Is there any other way to establish the connection? I am also providing my code below for reference.
mport javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
import javax.mail.Authenticator;
public class otp {
String d_email = "email#gmail.com",
d_password = "password",
d_uname="uname",//your email password
d_host = "mail.outlook.com",
d_port = "587",
m_to = "target#gmail.com", // Target email address
m_subject = "Testing Mail programs",
m_text = "Hey, this is a test email.";
public otp() {
Properties props = new Properties();
props.put("mail.smtp.user", d_email);
props.put("mail.smtp.host", d_host);
props.put("mail.smtp.port", d_port);
props.put("mail.smtp.starttls.enable", "true");
props.put("mail.smtp.debug", "true");
props.put("mail.smtp.socketFactory.port", d_port);
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.socketFactory.fallback", "false");
try {
Authenticator auth = new SMTPAuthenticator();
Session session = Session.getInstance(props,auth);
session.setDebug(true);
MimeMessage msg = new MimeMessage(session);
msg.setText(m_text);
msg.setSubject(m_subject);
System.out.println(1);
msg.setFrom(new InternetAddress(d_email));
msg.addRecipient(Message.RecipientType.TO, new InternetAddress(m_to));
System.out.println(3);
Transport transport = session.getTransport("smtp");
transport.connect(d_host, Integer.valueOf(d_port),d_uname , d_password);
transport.sendMessage(msg, msg.getAllRecipients());
transport.close();
Transport.send(msg);
System.out.println("Message Sent succesfully");
} catch (Exception mex) {
mex.printStackTrace();
}
}
public static void main(String[] args) {
otp blah = new otp();
}
private class SMTPAuthenticator extends javax.mail.Authenticator {
public PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(d_email, d_password);
}
}
}

I guess that you are behind the internal firewall/proxy of your office, it is very common to put the whole internal network of a company behind a central firewall or to check Outgoing/Incoming requests of the networks traffic a Dynamic Proxy Server.in that case, you can check it in the proxy settings of your pc.
internet explorer(or any browser)-> settings -> internet option -> Connections Tab -> LAN Settings.
for the granular analyses,please attach your code.

you are using a gmail account but you have provided a outlook host , try the following template:
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
public class SendEmailUsingGMailSMTP {
public static void main(String[] args) {
// Recipient's email ID needs to be mentioned.
String to = "xyz#gmail.com";//change accordingly
// Sender's email ID needs to be mentioned
String from = "abc#gmail.com";//change accordingly
final String username = "abc";//change accordingly
final String password = "*****";//change accordingly
// >> gmail host
String host = "smtp.gmail.com";
Properties props = new Properties();
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");
props.put("mail.smtp.host", host);
props.put("mail.smtp.port", "587");
// Get the Session object.
Session session = Session.getInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}
});
try {
// Create a default MimeMessage object.
Message message = new MimeMessage(session);
// Set From: header field of the header.
message.setFrom(new InternetAddress(from));
// Set To: header field of the header.
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse(to));
// Set Subject: header field
message.setSubject("Testing Subject");
// Now set the actual message
message.setText("Hello, this is sample for to check send "
+ "email using JavaMailAPI ");
// Send message
Transport.send(message);
System.out.println("Sent message successfully....");
} catch (MessagingException e) {
throw new RuntimeException(e);
}enter code here
}
}

Simple Java mail program is not working?

I am wondering why the below basic java mail program is not working because I didn't get any errors as the program is executed just fine. Is there anything that I am doing wrong? Any help would be appreciated.I would also like to add that I also tried it using wrong username and password combination but still getting no error and the programs runs completely fine.
public class emailfromgmail {
public static void main(String[]args)
{
final String from = "username";
final String pass = "password";
String to = "recipient#gmail.com";
String host="smtp.gmail.com";
String subject = "java Mail";
String body = "example of java mail api using gmail smtp";
//get the session object
Properties p = System.getProperties();
p.put("mail.smtp.starttls.enable","true");
p.put("mail.smtp.host",host);
p.put("mail.smtp.user",from);
p.put("mail.smtp.password",pass );
p.put("mail.smtp.port", "587");
p.put("mail.smtp.auth","true");
Session session = Session.getInstance(p,
new javax.mail.Authenticator() {
#Override
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(from, pass);
}
});
try{
MimeMessage msg = new MimeMessage(session);
msg.setFrom(new InternetAddress(from));
msg.addRecipient(Message.RecipientType.TO,new InternetAddress(to));
msg.setSubject(subject);
msg.setText(body);
Transport.send(msg);
System.out.print("message sent successfully");
}
catch(MessagingException e){
e.printStackTrace();
}
}
}

I had the same problem - I ran my program and put in a dialogue box in various places to see where it stopped doing anything. I still don't know what was wrong, but I tried a totally different approach and it worked. Instead of sending via TLS, I send via SSL. I used this website:
https://www.mkyong.com/java/javamail-api-sending-email-via-gmail-smtp-example/
Their TLS didn't work - it just didn't do anything when I ran it. Their SSL worked like a charm!
Here is the code:
package com.mkyong.common;
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
public class SendMailSSL {
public static void main(String[] args) {
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.socketFactory.class",
"javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.port", "465");
Session session = Session.getDefaultInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("username","password");
}
});
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("from#no-spam.com"));
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("to#no-spam.com"));
message.setSubject("Testing Subject");
message.setText("Dear Mail Crawler," +
"\n\n No spam to my email, please!");
Transport.send(message);
System.out.println("Done");
} catch (MessagingException e) {
throw new RuntimeException(e);
}
}
}

I have this code to send mail from java showing error

package Controller;
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
public class SendMail {
static String from = "******#gmail.com";
static String pass ="*****";
static String to = "****#gmail.com";
static String host = "smtp.gmail.com";
public static void main(String[] args) {
Properties properties = System.getProperties();
properties.put("mail.smtp.starttls.enable", "true");
properties.put("mail.smtp.host", host);
properties.put("mail.smtp.user", from);
properties.put("mail.smtp.password", pass);
properties.put("mail.smtp.port", "587");
properties.put("mail.smtp.auth", "true");
Session session = Session.getDefaultInstance(properties);
try{
MimeMessage message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO,
new InternetAddress(to));
message.setSubject("This is the Subject Line!");
message.setText("Ithis is a test");
Transport transport = session.getTransport("smtp");
transport.connect(host, from, pass);
transport.sendMessage(message, message.getAllRecipients());
transport.close();
System.out.println("Sent message successfully....");
}
catch (MessagingException mex) {
mex.printStackTrace();
}
}
}
This code shows the error of:
javax.mail.MessagingException: Could not convert socket to TLS;
Could anyone help me, why can't it convert socket to TLS. What can I do to resolve the error?? Please do help.

By default, Gmail does not allow "less-secure" Apps to access your email.
In order to get your code to run:
Sign into your gmail account in a browser.
Go to https://www.google.com/settings/security/lesssecureapps
Set the Access for less secure apps option to Turn on

Either the certificate has not been installed in file cacerts or you might want to set the google smtp url as "trusted". try add this code
properties.put("mail.smtp.ssl.trust", "smtp.gmail.com");
on the other note. You might need to set the javax.mail.Authenticator when you try to get the session

// Build session to create MimeMessage to send
Properties props = new Properties();
props.setProperty("mail.transport.protocol", "smtp");
props.setProperty("mail.host", "smtp.gmail.com");
props.put("mail.smtp.starttls.enable","true");
props.put("mail.smtp.ssl.enable", "true");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.port", "587");
props.setProperty("mail.smtp.quitwait", "false");
Session session = Session.getDefaultInstance(props, new Authenticator() {
#Override
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("name_here", "password_here");
}
});

java: Sending failed

After multiple researches I can't succeed to send any mail with java
Properties props = new Properties();
props.put("mail.smtp.starttls.enable", "true");
props.put("mail.smtp.starttls.required", "true");
props.put("mail.transport.protocol","smtp");
props.put("mail.smtp.host", "smtp.live.com");
props.put("mail.smtp.port", "587");
Session session = Session.getDefaultInstance(props, null);
Message msg = new MimeMessage(session);
msg.setFrom(new InternetAddress("matr#live.fr"));
InternetAddress toAddress = new InternetAddress("matrphone#gmail.com");
msg.addRecipient(Message.RecipientType.TO, toAddress);
msg.setSubject("sujet du mail de text");
msg.setText("aaa");
Transport transport = session.getTransport("smtps");
transport.connect("smtp.gmail.com", 587,"matr#live.fr", "mypasswordcached");
transport.send(msg);
I have Exception in thread "main" javax.mail.NoSuchProviderException: No provider for smtps
I don't understand why
Anyone can help me please ?

Try the following code:
package org.kodejava.example.mail;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import java.util.Date;
import java.util.Properties;
public class GmailSendEmailTLS {
public static final String USERNAME = "username";
public static final String PASSWORD = "password";
public static void main(String[] args) throws Exception {
//
// Email information such as from, to, subject and contents.
//
String mailFrom = "email#gmail.com";
String mailTo = "email#gmail.com";
String mailSubject = "TLS - Gmail Send Email Demo";
String mailText = "TLS - Gmail Send Email Demo";
GmailSendEmailTLS gmail = new GmailSendEmailTLS();
gmail.sendMail(mailFrom, mailTo, mailSubject, mailText);
}
private void sendMail(String mailFrom, String mailTo,
String mailSubject, String mailText)
throws Exception {
Properties config = createConfiguration();
//
// Creates a mail session. We need to supply username and
// password for Gmail authentication.
//
Session session = Session.getInstance(config, new Authenticator() {
#Override
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(
GmailSendEmailTLS.USERNAME,
GmailSendEmailTLS.PASSWORD
);
}
});
//
// Creates email message
//
Message message = new MimeMessage(session);
message.setSentDate(new Date());
message.setFrom(new InternetAddress(mailFrom));
message.setRecipient(Message.RecipientType.TO,
new InternetAddress(mailTo));
message.setSubject(mailSubject);
message.setText(mailText);
//
// Send a message
//
Transport.send(message);
}
private Properties createConfiguration() {
return new Properties() {{
put("mail.smtp.auth", "true");
put("mail.smtp.host", "smtp.gmail.com");
put("mail.smtp.port", "587");
put("mail.smtp.starttls.enable", "true");
}};
}
}
This example taken from: Sending email using gmail via TLS

Sending emails over SMTP with TSL

The code posted below works fine for me to send an email over an STMP with SSL.
Now the SMTP changed to TSL and i dont manage to send email with it.
I tried several things like adding
props.put("mail.smtp.starttls.enable","true");
but it was no use.
The error code says:
"javax.mail.MessagingException: Could not connect to SMTP host: exch.studi.fhws.de, port: 587;
nested exception is:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?"
Any ideas?
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
public class SendMail
{
String d_email = "...",
password = "...",
host = "...",
port = "25",
mailTo = "...",
mailSubject = "test",
mailText = "test";
public SendMail()
{
Properties props = new Properties();
props.put("mail.smtp.user", d_email);
props.put("mail.smtp.host", host);
props.put("mail.smtp.port", port);
props.put("mail.smtp.starttls.enable","true");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.socketFactory.port", port);
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.socketFactory.fallback", "false");
SecurityManager security = System.getSecurityManager();
try
{
Authenticator auth = new SMTPAuthenticator();
Session session = Session.getInstance(props, auth);
MimeMessage msg = new MimeMessage(session);
msg.setText(mailText);
msg.setSubject(mailSubject);
msg.setFrom(new InternetAddress(d_email));
msg.addRecipient(Message.RecipientType.TO, new InternetAddress(mailTo));
Transport.send(msg);
}
catch (Exception mex)
{
mex.printStackTrace();
}
}
public static void main(String[] args)
{
TextClass tc = new TextClass();
}
private class SMTPAuthenticator extends javax.mail.Authenticator
{
public PasswordAuthentication getPasswordAuthentication()
{
return new PasswordAuthentication(d_email, password);
}
}
}

The error message says you're connecting to port 587 - this is an SSL-enabled email port, which means the connection has to be SSL from the get-go. Your code is connecting via plaintext (e.g. plain port 25) and THEN attempting to start TLS. This won't work, as port 587 expects an SSL exchange immediately, not a "EHLO ... / STARTTLS" plaintext command set.

Maybe this answer, talking about Exchange servers with SMTP ports disabled, is useful: https://stackoverflow.com/a/12631772/187148