why is my sending mail not working from MFMailComposeViewController?

I found this source code from here and tried sending mail using it. I successfully got the 'MFMailComposeResultSent' Message, but actual mail is not sent. I don't understand why is not working. Also, I attached an image from NSData, but it doesn't display in mailcomposeview. What is the wrong with this code? Actually, I only need calling native mail app with an attachement image, but I heard there is no way calling the native app with attachement. Please let me know what is wrong with my code. Problem 1: doesn't send a mail from mailcomposeview, Problem 2: doesn't display attached image. Best : running native mail app with attached image. I'll be happily waiting your answers. Thx.

-(void) sendMail
{
NSLog(@"Mail");
MFMailComposeViewController *mfMailView = [[MFMailComposeViewController alloc]init];
NSData *imgData = UIImagePNGRepresentation(imgPreview.image);
mfMailView.mailComposeDelegate = self;

[mfMailView addAttachmentData:imgData mimeType:@"image/png" fileName:@"Me.png"];

//also tried this
//[mfMailView addAttachmentData:imgData mimeType:@"image/png" fileName:@"Me"];

[mfMailView setSubject:@"TE~st"];

[mfMailView setMessageBody:@"Download Me~!" isHTML:YES];
[self presentModalViewController:mfMailView animated:YES];
}

-(void) mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError *)error
{
switch (result) {
    case MFMailComposeResultCancelled:
        NSLog(@"cancel?");
        break;
    case MFMailComposeResultSaved:
        NSLog(@"saved?");
        break;
    case MFMailComposeResultSent:
        NSLog(@"Sent succed");
        [controller dismissModalViewControllerAnimated:YES];
        break;
    case MFMailComposeResultFailed:
        NSLog(@"sent failue");
        NSLog(@"%@",error);
        break;
    default:
        break;
}
}

1. Make sure that you have an account configured in the settings.
2. I didn't find any recipient??

You can take a reference from this link.