如果你想从你的应用程序发送电子邮件，上面的代码是唯一的方法，除非你在你的应用程序内编写自己的邮件客户端(SMTP)，或者有一个服务器为你发送邮件。

例如，你可以编写你的应用程序来调用服务器上的URL，它会为你发送邮件。然后只需从代码中调用URL。

请注意，使用上面的代码，您不能向电子邮件附加任何内容，而SMTP客户端方法和服务器端方法允许您这样做。

斯威夫特2.0

func mailComposeController(controller: MFMailComposeViewController, didFinishWithResult result: MFMailComposeResult, error: NSError?){
    if let error = error{
        print("Error: \(error)")
    }else{
        //NO Error
        //------------------------------------------------
        var feedbackMsg = ""

        switch result.rawValue {
        case MFMailComposeResultCancelled.rawValue:
            feedbackMsg = "Mail Cancelled"
        case MFMailComposeResultSaved.rawValue:
            feedbackMsg = "Mail Saved"
        case MFMailComposeResultSent.rawValue:
            feedbackMsg = "Mail Sent"
        case MFMailComposeResultFailed.rawValue:
            feedbackMsg = "Mail Failed"
        default:
            feedbackMsg = ""
        }

        print("Mail: \(feedbackMsg)")

        //------------------------------------------------
    }
}

MFMailComposeViewController是iPhone OS 3.0软件发布后的一种方式。您可以查看示例代码或我编写的教程。

这是可以帮助你的代码，但不要忘记包括消息ui framewark和包括委托方法MFMailComposeViewControllerDelegate

-(void)EmailButtonACtion{

        if ([MFMailComposeViewController canSendMail])
        {
            MFMailComposeViewController *controller = [[MFMailComposeViewController alloc] init];
            controller.mailComposeDelegate = self;
            [controller.navigationBar setBackgroundImage:[UIImage imageNamed:@"navigation_bg_iPhone.png"] forBarMetrics:UIBarMetricsDefault];
            controller.navigationBar.tintColor = [UIColor colorWithRed:51.0/255.0 green:51.0/255.0 blue:51.0/255.0 alpha:1.0];
            [controller setSubject:@""];
            [controller setMessageBody:@" " isHTML:YES];
            [controller setToRecipients:[NSArray arrayWithObjects:@"",nil]];
            UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];
            UIImage *ui = resultimg.image;
            pasteboard.image = ui;
            NSData *imageData = [NSData dataWithData:UIImagePNGRepresentation(ui)];
            [controller addAttachmentData:imageData mimeType:@"image/png" fileName:@" "];
            [self presentViewController:controller animated:YES completion:NULL];
        }
        else{
            UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"alrt" message:nil delegate:self cancelButtonTitle:@"ok" otherButtonTitles: nil] ;
            [alert show];
        }

    }
    -(void)mailComposeController:(MFMailComposeViewController*)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError*)error
    {

        [MailAlert show];
        switch (result)
        {
            case MFMailComposeResultCancelled:
                MailAlert.message = @"Email Cancelled";
                break;
            case MFMailComposeResultSaved:
                MailAlert.message = @"Email Saved";
                break;
            case MFMailComposeResultSent:
                MailAlert.message = @"Email Sent";
                break;
            case MFMailComposeResultFailed:
                MailAlert.message = @"Email Failed";
                break;
            default:
                MailAlert.message = @"Email Not Sent";
                break;
        }
        [self dismissViewControllerAnimated:YES completion:NULL];
        [MailAlert show];
    }

这里我想补充几点:

使用mailto URL在模拟器中不能作为邮件工作。应用程序未安装在模拟器上。但它在设备上确实有效。 mailto URL的长度有限制。如果URL大于4096个字符，请发送邮件。应用程序无法启动。 OS 3.0中有一个新类，可以让你在不离开应用程序的情况下发送电子邮件。请看类MFMailComposeViewController。

在ios3.0及以后的版本中，你应该使用MFMailComposeViewController类，以及隐藏在MessageUI框架中的MFMailComposeViewControllerDelegate协议。

首先添加框架并导入:

#import <MessageUI/MFMailComposeViewController.h>

然后，发送一个消息:

MFMailComposeViewController* controller = [[MFMailComposeViewController alloc] init];
controller.mailComposeDelegate = self;
[controller setSubject:@"My Subject"];
[controller setMessageBody:@"Hello there." isHTML:NO]; 
if (controller) [self presentModalViewController:controller animated:YES];
[controller release];

然后用户完成工作，你及时得到委托回调:

- (void)mailComposeController:(MFMailComposeViewController*)controller  
          didFinishWithResult:(MFMailComposeResult)result 
                        error:(NSError*)error;
{
  if (result == MFMailComposeResultSent) {
    NSLog(@"It's away!");
  }
  [self dismissModalViewControllerAnimated:YES];
}

记得检查设备是否配置为发送电子邮件:

if ([MFMailComposeViewController canSendMail]) {
  // Show the composer
} else {
  // Handle the error
}