斯威夫特2.2。改编自Esq的回答

import Foundation
import MessageUI

class MailSender: NSObject, MFMailComposeViewControllerDelegate {

    let parentVC: UIViewController

    init(parentVC: UIViewController) {
        self.parentVC = parentVC
        super.init()
    }

    func send(title: String, messageBody: String, toRecipients: [String]) {
        if MFMailComposeViewController.canSendMail() {
            let mc: MFMailComposeViewController = MFMailComposeViewController()
            mc.mailComposeDelegate = self
            mc.setSubject(title)
            mc.setMessageBody(messageBody, isHTML: false)
            mc.setToRecipients(toRecipients)
            parentVC.presentViewController(mc, animated: true, completion: nil)
        } else {
            print("No email account found.")
        }
    }

    func mailComposeController(controller: MFMailComposeViewController,
        didFinishWithResult result: MFMailComposeResult, error: NSError?) {

            switch result.rawValue {
            case MFMailComposeResultCancelled.rawValue: print("Mail Cancelled")
            case MFMailComposeResultSaved.rawValue: print("Mail Saved")
            case MFMailComposeResultSent.rawValue: print("Mail Sent")
            case MFMailComposeResultFailed.rawValue: print("Mail Failed")
            default: break
            }

            parentVC.dismissViewControllerAnimated(false, completion: nil)
    }
}

客户端代码:

var ms: MailSender?

@IBAction func onSendPressed(sender: AnyObject) {
    ms = MailSender(parentVC: self)
    let title = "Title"
    let messageBody = "https://stackoverflow.com/questions/310946/how-can-i-send-mail-from-an-iphone-application this question."
    let toRecipents = ["foo@bar.com"]
    ms?.send(title, messageBody: messageBody, toRecipents: toRecipents)
}

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
}

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。

下面的代码在我的应用程序中用于发送带有附件的电子邮件这里的附件是一张图片，你可以发送任何类型的文件唯一需要记住的是你必须指定正确的mimeType

将此添加到.h文件中

#import <MessageUI/MFMailComposeViewController.h>

将MessageUI.framework添加到项目文件中

NSArray *paths = SSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];

NSString *getImagePath = [documentsDirectory stringByAppendingPathComponent:@"myGreenCard.png"];



MFMailComposeViewController* controller = [[MFMailComposeViewController alloc] init];
controller.mailComposeDelegate = self;
[controller setSubject:@"Green card application"];
[controller setMessageBody:@"Hi , <br/>  This is my new latest designed green card." isHTML:YES]; 
[controller addAttachmentData:[NSData dataWithContentsOfFile:getImagePath] mimeType:@"png" fileName:@"My Green Card"];
if (controller)
    [self presentModalViewController:controller animated:YES];
[controller release];

委托方法如下所示

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