Determines whether the email address is a real address.
import java.io.*;import java.net.*;import java.util.*;import javax.naming.*;import javax.naming.directory.*;public class SMTPMXLookup { 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 mailhost; String x = (String) en.next(); String f[] = x.split( " " ); // THE fix ************* if (f.length == 1) mailhost = f[0]; else if ( f[1].endsWith( "." ) ) mailhost = f[1].substring( 0, (f[1].length() - 1)); else mailhost = f[1]; // THE fix ************* res.add( mailhost ); } 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 rgagnon.com" ); res = hear( rdr ); if ( res != 250 ) throw new Exception( "Not ESMTP" ); // validate the sender address say( wtr, "MAIL FROM:
" ); 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 ex.printStackTrace(); } finally { if ( valid ) return true; } } return false; } public static void main( String args[] ) { String testData[] = { "real@rgagnon.com", "you@acquisto.net", "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; }}