MimeMessage msg = mailSender.createMimeMessage();
            try {
                MimeMessageHelper helper = new MimeMessageHelper(msg, true);
                helper.setFrom("from@from.com");
                helper.setTo("to@to.com");
                helper.setSubject("ENCRYPTED MAIL TEST");
                helper.setText(BouncyCrypt.encryptString(                                    
                                    "crypted mail test text...", 
                                    BouncyCrypt.readPublicKey("G:\\public_key\\encrypt.asc")));
                helper.addAttachment("attachment.txt", new File(filePath")); 
                
                mailSender.send(msg);
                
            } catch(MessagingException | MailException ex) {
                ex.printStackTrace();
            }

    public static String encryptString(String clearData, PGPPublicKey encKey) throws IOException, NoSuchProviderException, PGPException {
        return new String(encryptBytes(clearData.getBytes(), encKey));
    }    
    
    
    private static byte[] encryptBytes(byte[] clearData, PGPPublicKey encKey) throws IOException, NoSuchProviderException, PGPException {
        String fileName = PGPLiteralData.CONSOLE;
        
        ByteArrayOutputStream encOut = new ByteArrayOutputStream();
        OutputStream out = new ArmoredOutputStream(encOut);
        
        ByteArrayOutputStream bOut = new ByteArrayOutputStream();

        PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedDataGenerator.ZIP);
        
        OutputStream cos = comData.open(bOut);
        PGPLiteralDataGenerator lData = new PGPLiteralDataGenerator();

        OutputStream pOut = lData.open(
                cos,
                PGPLiteralData.BINARY, fileName,
                clearData.length,
                new java.util.Date()
                );
        pOut.write(clearData);

        lData.close();
        comData.close();
        
        JcePGPDataEncryptorBuilder c = new JcePGPDataEncryptorBuilder(PGPEncryptedData.CAST5).setWithIntegrityPacket(true).setSecureRandom(new SecureRandom()).setProvider("BC");        
        PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(c);        

        cPk.addMethod(new JcePublicKeyKeyEncryptionMethodGenerator(encKey).setProvider(new BouncyCastleProvider()).setSecureRandom(new SecureRandom()));

        byte[] bytes = bOut.toByteArray();

        OutputStream cOut = cPk.open(out, bytes.length);

        cOut.write(bytes); // obtain the actual bytes from the compressed stream

        cOut.close();

        out.close();

        return encOut.toByteArray();
    }   

    static PGPPublicKey readPublicKey(String fileName) throws IOException, PGPException
    {
        PGPPublicKey pubKey;
        try (InputStream keyIn = new BufferedInputStream(new FileInputStream(fileName))) {
            pubKey = readPublicKey(keyIn);
        }
        return pubKey;
    }

public static void encryptFile(OutputStream out, String fileName, PGPPublicKey encKey, boolean armor, boolean withIntegrityCheck) throws IOException, NoSuchProviderException, PGPException {
    	
        Security.addProvider(new BouncyCastleProvider());

        if (armor) { out = new ArmoredOutputStream(out); }

        ByteArrayOutputStream bOut = new ByteArrayOutputStream();

        PGPCompressedDataGenerator comData = new PGPCompressedDataGenerator(PGPCompressedData.ZIP);

        PGPUtil.writeFileToLiteralData(comData.open(bOut), PGPLiteralData.BINARY, new File(fileName));

        comData.close();

        JcePGPDataEncryptorBuilder c = new JcePGPDataEncryptorBuilder(PGPEncryptedData.CAST5).setWithIntegrityPacket(withIntegrityCheck).setSecureRandom(new SecureRandom()).setProvider("BC");
        
        PGPEncryptedDataGenerator cPk = new PGPEncryptedDataGenerator(c);
        
        JcePublicKeyKeyEncryptionMethodGenerator d = new JcePublicKeyKeyEncryptionMethodGenerator(encKey).setProvider(new BouncyCastleProvider()).setSecureRandom(new SecureRandom());

        cPk.addMethod(d);

        byte[] bytes = bOut.toByteArray();

        OutputStream cOut = cPk.open(out, bytes.length);

        cOut.write(bytes);

        cOut.close();

        out.close();
    }

MimeMessageHelper helper = new MimeMessageHelper(msg, 1);

                helper.addAttachment("attachment.txt", new File(filePath")); 
                helper.setText(BouncyCrypt.encryptString(                                    
                                    "crypted mail test text...", 
                                    BouncyCrypt.readPublicKey("G:\\public_key\\encrypt.asc")));