java send email

public boolean sendEMail( String sender,EmailArtifact artifact)  throws InvalidEmailAddressException, SendEmailException
    {

        try {

            javax.mail.Session session =null;

            if(StringUtils.isBlank(username)){
                session  = Session.getInstance(props, null);
            }else{
                /**
                 * Using Default session generates an error : access to Default Session denied~
                 * It seems the appserver already created a session using Session.getDefaultSession
                 * which is denying us access to it
                 */
                session= javax.mail.Session.getInstance( props,
                        new Authenticator (  )   {
                                public PasswordAuthentication getPasswordAuthentication (  )   {
                                    return new PasswordAuthentication ( username, password ) ;
                                }
                        }  );
            }


            MimeMessage message = new MimeMessage( session );
            message.setFrom(new InternetAddress( sender ));
            message.setHeader("Content-Type","text/plain; charset=\"UTF-8\"");
            message.setHeader("Content-Transfer-Encoding", "quoted-printable");
            if (artifact.getTo() != null) {
                for ( Iterator<String> it = artifact.getTo().iterator() ; it.hasNext() ; )
                    message.addRecipient(
                            javax.mail.Message.RecipientType.TO,
                            new InternetAddress( (String) it.next() )
                    );
            }

            if (artifact.getCc() != null) {
                for ( Iterator<String> it = artifact.getCc().iterator() ; it.hasNext() ; )
                    message.addRecipient(
                            javax.mail.Message.RecipientType.CC,
                            new InternetAddress( (String) it.next() )
                    );
            }

            if (artifact.getBcc() != null) {
                for ( Iterator<String> it = artifact.getBcc().iterator() ; it.hasNext() ; )
                    message.addRecipient(
                            javax.mail.Message.RecipientType.BCC,
                            new InternetAddress( (String) it.next() )
                    );
            }

            message.setSubject( artifact.getSubject() ,"UTF-8");
            message.setSentDate ( new Date()) ;

            // create and fill the first message part
            MimeBodyPart mbp1 = new MimeBodyPart (  ) ;

            mbp1.setContent(artifact.getBody() +"\n\n"+artifact.getSignature(), "text/plain; charset=UTF-8");

            mbp1.setHeader("Content-Type","text/plain; charset=UTF-8");
            mbp1.setHeader("Content-Transfer-Encoding", "quoted-printable");
            Multipart mp = new MimeMultipart (  ) ;
            mp.addBodyPart ( mbp1 ) ;
            for (Entry<String, byte[]> att : artifact.getAttachments().entrySet()) {
                MimeBodyPart attachment = new MimeBodyPart (  ) ;
                attachment.setDataHandler ( new DataHandler ( new ByteArrayDataSource(att.getValue(),"application/octet-stream") ) );
                attachment.setFileName(att.getKey());
                mp.addBodyPart ( attachment ) ;
            }


            // add the Multipart to the message
            message.setContent ( mp) ;

            Transport.send( message );

            return true;
        }
        catch ( AddressException e )
        {
            throw new InvalidEmailAddressException(e.getMessage());
        }
        catch ( MessagingException e )
        {
            throw new SendEmailException(e);
        }
    }