how can check pragmatically yahoo email exist or not exist?

I`m write this code for check yahoo account but cant response yahoo ? i need write service like this site (verifyemailaddress.io) The best you can do to verify if an email address is real is to verify if there is a mail server registered to the domain name. While using the code I noticed a problem with greylisting. Greylisting, is an anti spam attempt which denies service for the first time the triple of client, sender and address reaches the smtp server. Greylisting will send back a temporary error (450) and therefore the address will be denied. In this case it probably is better to accept the address as verified, because there is no better information available at that moment. import java.io.; import java.net.; import java.util.; import javax.naming.; import javax.naming.directory.*;

public class SMTP {
    private static int hear( BufferedReader in ) throws IOException {
    String line = null;
    int res = 0;

    while ( (line = in.readLine()) != null ) {
        String pfx = line.substring( 0, 3 );
        try {
            res = Integer.parseInt( pfx );
        } 
        catch (Exception ex) {
            res = -1;
        }
        if ( line.charAt( 3 ) != '-' ) break;
    }

    return res;
    }

    private static void say( BufferedWriter wr, String text ) 
    throws IOException {
    wr.write( text + "\r\n" );
    wr.flush();

    return;
    }

    private static ArrayList getMX( String hostName )
        throws NamingException {
    // Perform a DNS lookup for MX records in the domain
    Hashtable env = new Hashtable();
    env.put("java.naming.factory.initial",
            "com.sun.jndi.dns.DnsContextFactory");
    DirContext ictx = new InitialDirContext( env );
    Attributes attrs = ictx.getAttributes
                            ( hostName, new String[] { "MX" });
    Attribute attr = attrs.get( "MX" );

    // if we don't have an MX record, try the machine itself
    if (( attr == null ) || ( attr.size() == 0 )) {
        attrs = ictx.getAttributes( hostName, new String[] { "A" });
        attr = attrs.get( "A" );
        if( attr == null ) 
            throw new NamingException
                    ( "No match for name '" + hostName + "'" );
    }

    // Huzzah! we have machines to try. Return them as an array list
    // NOTE: We SHOULD take the preference into account to be absolutely
    //   correct. This is left as an exercise for anyone who cares.
    ArrayList res = new ArrayList();
    NamingEnumeration en = attr.getAll();

    while ( en.hasMore() ) {
        String x = (String) en.next();
        String f[] = x.split( " " );
        if ( f[1].endsWith( "." ) ) 
            f[1] = f[1].substring( 0, (f[1].length() - 1));
        res.add( f[1] );
    }
    return res;
    }

    public static boolean isAddressValid( String address ) {
    // Find the separator for the domain name
    int pos = address.indexOf( '@' );

    // If the address does not contain an '@', it's not valid
    if ( pos == -1 ) return false;

    // Isolate the domain/machine name and get a list of mail exchangers
    String domain = address.substring( ++pos );
    ArrayList mxList = null;
    try {
        mxList = getMX( domain );
    } 
    catch (NamingException ex) {
        return false;
    }

    // Just because we can send mail to the domain, doesn't mean that the
    // address is valid, but if we can't, it's a sure sign that it isn't
    if ( mxList.size() == 0 ) return false;

    // Now, do the SMTP validation, try each mail exchanger until we get
    // a positive acceptance. It *MAY* be possible for one MX to allow
    // a message [store and forwarder for example] and another [like
    // the actual mail server] to reject it. This is why we REALLY ought
    // to take the preference into account.
    for ( int mx = 0 ; mx < mxList.size() ; mx++ ) {
        boolean valid = false;
        try {
            int res;
            Socket skt = new Socket( (String) mxList.get( mx ), 25 );
            BufferedReader rdr = new BufferedReader
                ( new InputStreamReader( skt.getInputStream() ) );
            BufferedWriter wtr = new BufferedWriter
                ( new OutputStreamWriter( skt.getOutputStream() ) );

            res = hear( rdr );
            if ( res != 220 ) throw new Exception( "Invalid header" );
            say( wtr, "EHLO orbaker.com" );

            res = hear( rdr );
            if ( res != 250 ) throw new Exception( "Not ESMTP" );

            // validate the sender address  
            say( wtr, "MAIL FROM: <tim@orbaker.com>" );
            res = hear( rdr );
            if ( res != 250 ) throw new Exception( "Sender rejected" );

            say( wtr, "RCPT TO: <" + address + ">" );
            res = hear( rdr );

            // be polite
            say( wtr, "RSET" ); hear( rdr );
            say( wtr, "QUIT" ); hear( rdr );
            if ( res != 250 ) 
                throw new Exception( "Address is not valid!" );

            valid = true;
            rdr.close();
            wtr.close();
            skt.close();
        } 
        catch (Exception ex) {
            // Do nothing but try next host
        } 
        finally {
            if ( valid ) return true;
        }
    }
    return false;
    }

    public static void main( String args[] ) {
    String testData[] = {
        "tim@orbaker.com", // Valid address
        "fail.me@nowhere.spam", // Invalid domain name
        "arkham@bigmeanogre.net", // Invalid address
        "nosuchaddress@yahoo.com" // Failure of this method
        };

    for ( int ctr = 0 ; ctr < testData.length ; ctr++ ) {
        System.out.println( testData[ ctr ] + " is valid? " + 
            isAddressValid( testData[ ctr ] ) );
    }
    return;
    }
}

how can check yahoo account can guide me ?