MFMailComposeViewController不是交互式的

if ([MFMailComposeViewController canSendMail]) {
    MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
    picker.mailComposeDelegate = self;

    [picker setSubject:@"Message subject"];
    [picker setMessageBody:@"Sample message" isHTML:NO];

    [self presentModalViewController:picker animated:YES];

    [picker release];
} else {
    NSLog(@"cant send mail");
}