this is the code to send a mail with attachment
import java.io.File;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class sendemail extends Activity {

    Button send;

    EditText address, subject, emailtext;

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.main11);

    send = (Button) findViewById(R.id.emailsendbutton);

    address = (EditText) findViewById(R.id.emailaddress);

    subject = (EditText) findViewById(R.id.emailsubject);

    emailtext = (EditText) findViewById(R.id.emailtext);

    final TextView tv = (TextView)findViewById(R.id.fileContent);

    send.setOnClickListener(new OnClickListener() {

   // TextView tv = (TextView)findViewById(R.id.fileContent);
    public void onClick(View v) {

    // TODO Auto-generated method stub

        if(!address.getText().toString().trim().equalsIgnoreCase("")){
        //    Toast.makeText(getApplicationContext(), "Please enter an
email address..", Toast.LENGTH_LONG).show();

              File dir = Environment.getExternalStorageDirectory();
                           File file = new
File(dir,"download/phonedata.txt");
                         if (file.exists())

                    try {
                  Log.i(getClass().getSimpleName(), "send  task - start");
                final Intent emailIntent = new Intent(
                android.content.Intent.ACTION_SEND);
                emailIntent.setType("plain/text");
            //    emailIntent.setType("application/octet-stream");

                emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL,new
String[] { address.getText().toString() });

                emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT,
subject.getText());

                emailIntent.putExtra(Intent.EXTRA_STREAM,
                Uri.parse("file://" + file));
                Toast.makeText(sendemail.this, "File successfully attached
in your Mail!!!",
                        Toast.LENGTH_LONG).show();
                tv.setText("File Successfully attached in your mail!!!");
                emailIntent.putExtra(android.content.Intent.EXTRA_TEXT,
emailtext.getText());

                sendemail.this.startActivity(Intent
                .createChooser(emailIntent, "Send mail..."));

                } catch (Throwable t) {

                Toast.makeText(sendemail.this, "Request failed: " +
t.toString(),
                Toast.LENGTH_LONG).show();
                }
                else
                {
                    tv.setText("Sorry file doesn't exist!!!");
                    Toast.makeText(sendemail.this, "File not found in
sd-card....Please upload it from Server!!!",
                              Toast.LENGTH_LONG).show();
                    //Toast.makeText(getApplicationContext(), "Please enter
an email address..", Toast.LENGTH_LONG).show();
                }
                }
                else
                {
                   Toast.makeText(getApplicationContext(), "Please enter an
email address..", Toast.LENGTH_LONG).show();}
                 }
        });
        }
    }
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xml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="@+id/LinearLayout01"

android:layout_width="fill_parent" android:layout_height="fill_parent"

xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical"
android:background="#6699FF">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text=""
android:id="@+id/fileContent" />

<LinearLayout android:id="@+id/LinearLayout02"

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:orientation="horizontal">

<EditText android:layout_width="wrap_content"

android:layout_height="wrap_content" android:width="170dip"

android:id="@+id/emailaddress"></EditText>

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/emailaddress"

android:text="Email address"></TextView>

</LinearLayout>

<LinearLayout android:id="@+id/LinearLayout03"

android:layout_width="wrap_content" android:layout_height="wrap_content"

android:orientation="horizontal">

<EditText android:layout_width="wrap_content"

android:layout_height="wrap_content" android:width="170dip"

android:id="@+id/emailsubject"></EditText>

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/emailsubject"

android:text="Subject"></TextView>

</LinearLayout>

<EditText android:layout_width="wrap_content"

android:layout_height="wrap_content" android:lines="5"
android:width="300dip"

android:id="@+id/emailtext"></EditText>

<Button android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/emailsendbutton"

android:text="Send!" android:width="150dip"></Button>

</LinearLayout>
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dont forget to add internet permission in your android manifest file
PS for sending a mail test this code on real device not on emulator