ios - MFMailComposeViewController - ViewController を提示できません

Question

これが私のコードです

-(IBAction)emailButtonPressed :(UIButton *)sender {

    if (![MFMailComposeViewController canSendMail]) {

        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil message:@"Mail has not been set up on this device" delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
        [alertView show];

        return;
}

    NSString *targetFile = [self saveCompleteImage];

    MFMailComposeViewController *mailpicker = [[MFMailComposeViewController alloc] init];
    [mailpicker setMailComposeDelegate:self];

    NSString *mimeType = [StringHelper getMimeType:targetFile];
    [mailpicker addAttachmentData:[NSData dataWithContentsOfFile:targetFile] mimeType:mimeType fileName:[targetFile lastPathComponent]];

    [mailpicker setSubject:[self.currentDocument getNameForUntitled]];
    mailpicker.modalPresentationStyle = UIModalPresentationFormSheet;

    [self.presentedViewController presentViewController:mailpicker animated:YES completion:nil];
}

メールピッカーを提示していません。どこが間違っているのか教えてください。