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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
}
}

Could not connect to SMTP host: smtp.gmail.com, port: 465, response: -1 why 465 is not working

i want create email template , in that i want append html code to create a template ,so i tried below code where in this port 465 number is not working
can any one helps me?
package com.indoabus2.mail;
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 SendHTMLEmail {
public static void main(String[] args) {
// Recipient's email ID needs to be mentioned.
String to = "vpenchalaprasad2#gmail.com";
// Sender's email ID needs to be mentioned
String from = "vpenchalaprasad2#gmail.com";
final String username = "vpenchalaprasad2";//change accordingly
final String password = "100509732041";//change accordingly
// Assuming you are sending email through relay.jangosmtp.net
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", "465");
// 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");
// Send the actual HTML message, as big as you like
message.setContent(
"<h1>This is actual message embedded in HTML tags</h1>",
"text/html");
// Send message
Transport.send(message);
System.out.println("Sent message successfully....");
} catch (MessagingException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
}
nut the code is not getting executed exception is
javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 465, response: -1
i am not able to trace it why 465 is not working , and what is response: -1can any one suggest me a solution

Google SMTP requires SSL instead of STARTTLS for port 465.
Just remove:
props.put("mail.smtp.starttls.enable", "true");
and add in to use SSL:
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
Or you can just change the port to 587.
https://support.google.com/a/answer/176600?hl=en-EN

The security file in my jre 1.8 was not allowing it to connect
I used the corretto jre 1.8 version and it worked.
This answer is coming after 2 days of visiting this and possible clones of this answer.
The file in question here for me was in the path $JAVA_HOME/lib/security/java.security
EDIT: there was a java 1.8 security release on april 20th 2021
this solution is only valid for people who are having issues after that

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

I don't get the e-mail using this code. What is the problem?

The following is the program, which I am trying to send e-mail. The code is error free and I don't get any run time exception. But the code is unable to send e-mail. I have revised this code a lot but can't get what is actually wrong.
The sender and the receiver both have GMail accounts. The sender has 2-step verification process disabled. (I don't think it matters for the receiver. Does it?)
The code :
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
class tester {
public static void main(String args[]) {
Properties props = new Properties();
props.put("mail.smtp.host" , "smtp.gmail.com");
props.put("mail.stmp.user" , "username"); // username or complete address ! Have tried both
Session session = Session.getDefaultInstance( props , null);
String to = "me#gmail.com";
String from = "from#gmail.com";
String subject = "Testing...";
Message msg = new MimeMessage(session);
try {
msg.setFrom(new InternetAddress(from));
msg.setRecipient(Message.RecipientType.TO , new InternetAddress(to));
msg.setSubject(subject);
msg.setText("Working fine..!");
System.out.println("fine!!??");
} catch(Exception exc) {
System.out.println(exc);
}
}
}

Well, your code doesn't actually attempt to send the message. Take a look at Transport.send.
Here are some examples:
http://www.javapractices.com/topic/TopicAction.do?Id=144
http://www.vipan.com/htdocs/javamail.html

First of all, you forgot to call Transport.send() to send your MimeMessage.
Secondly, GMail needs to be configured to use TLS or SSL connection. The following needs to be added to your Properties (props):
//To use TLS
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");
//To use SSL
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");
To connect to GMail SMTP, use the Transport.connect() method. I see you are not using any Transport at all in your code, so add this:
Transport transport = session.getTransport();
//Connect to GMail
transport.connect("smtp.gmail.com", 465, "USERNAME_HERE", "PASSWORD_HERE");
transport.send(msg);
Alternatively, you can create a Session by including a javax.mail.Authenticator as a parameter.
Example:
Session session = Session.getDefaultInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("USERNAME_HERE", "PASSWORD_HERE");
}
});
I hope this helps you.
Resources:
Send email with SMTPS (eg. Google GMail) (Javamail)
JavaMail API – Sending email via Gmail SMTP example

Sending email using SMTP

I am writing a simple Java program to send mail, but am getting errors. Here's the code:
package mypackage;
import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;
// Send a simple, single part, text/plain e-mail
public class Sendmail {
public static void main(String[] args) {
// SUBSTITUTE YOUR EMAIL ADDRESSES HERE!!!
String to = "atul.krbhatia#gmail.com";
String from = "atul.krbhatia#gmail.com";
// SUBSTITUTE YOUR ISP'S MAIL SERVER HERE!!!
String host = "smtp.gmail.com";
// Create properties, get Session
Properties props = new Properties();
// If using static Transport.send(),
// need to specify which host to send it to
props.put("mail.smtp.host", host);
// To see what is going on behind the scene
props.put("mail.debug", "true");
Session session = Session.getInstance(props);
try {
// Instantiatee a message
Message msg = new MimeMessage(session);
System.out.println("in try blk");
//Set message attributes
msg.setFrom(new InternetAddress(from));
InternetAddress[] address = {new InternetAddress(to)};
msg.setRecipients(Message.RecipientType.TO, address);
msg.setSubject("Test E-Mail through Java");
msg.setSentDate(new Date());
// Set message content
msg.setText("This is a test of sending a " +
"plain text e-mail through Java.\n" +
"Here is line 2.");
//Send the message
Transport.send(msg);
}
catch (MessagingException mex) {
// Prints all nested (chained) exceptions as well
System.out.println("in catch block");
mex.printStackTrace();
}
}
}//End of class
Here's the errors:
221 2.0.0 closing connection d1sm3094152pbj.24
in catch block
com.sun.mail.smtp.SMTPSendFailedException: 530 5.7.0 Must issue a STARTTLS command first. d1sm3094152pbj.24
at com.sun.mail.smtp.SMTPTransport.issueSendCommand(SMTPTransport.java:2057)
at com.sun.mail.smtp.SMTPTransport.mailFrom(SMTPTransport.java:1580)
at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1097)
at javax.mail.Transport.send0(Transport.java:195)
at javax.mail.Transport.send(Transport.java:124)
at mypackage.Sendmail.main(Sendmail.java:48)

Gmail only supports SMTP over SSL/TLS.
Add
props.put("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.socketFactory.fallback", "false");
You also need to login to the server:
props.put("mail.smtp.host", "smtp.gmail.com");
Session session = Session.getDefaultInstance(props, new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("username", "password");
}
});

A simple google search for "javamail gmail" will yield many example of how to use JavaMail with GMail, like this one. Google also has a configuration page listing the connection configuration that you'll need so you can double check the settings.

This URL May help:
http://sbtourist.blogspot.com/2007/10/javamail-and-gmail-its-all-about.html

It looks like the server is expecting SSL. There are several other questions on here where people are also trying to send mail through Gmail using Java, I recommend taking a look at them.
How can I send an email by Java application using GMail, Yahoo, or Hotmail?
Must issue a STARTTLS command first. Sending email with Java and Google Apps