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。

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)")

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

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。

以下是Swift版本:

import MessageUI

class YourVC: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        if MFMailComposeViewController.canSendMail() {
            var emailTitle = "Vea Software Feedback"
            var messageBody = "Vea Software! :) "
            var toRecipents = ["pj@veasoftware.com"]
            var mc:MFMailComposeViewController = MFMailComposeViewController()
            mc.mailComposeDelegate = self
            mc.setSubject(emailTitle)
            mc.setMessageBody(messageBody, isHTML: false)
            mc.setToRecipients(toRecipents)
            self.presentViewController(mc, animated: true, completion: nil)
        } else {
            println("No email account found")
        }
    }
}

extension YourVC: MFMailComposeViewControllerDelegate {
    func mailComposeController(controller: MFMailComposeViewController!, didFinishWithResult result: MFMailComposeResult, error: NSError!) {
        switch result.value {
        case MFMailComposeResultCancelled.value:
            println("Mail Cancelled")
        case MFMailComposeResultSaved.value:
            println("Mail Saved")
        case MFMailComposeResultSent.value:
            println("Mail Sent")
        case MFMailComposeResultFailed.value:
            println("Mail Failed")
        default:
            break
        }
        self.dismissViewControllerAnimated(false, completion: nil)
    }
}

源

从iPhone应用程序发送电子邮件，你需要做下面的任务列表。

步骤1:导入# Import <MessageUI/MessageUI.h>在你想要发送电子邮件的控制器类中。

步骤2:添加委托到您的控制器如下所示

 @interface <yourControllerName> : UIViewController <MFMessageComposeViewControllerDelegate, MFMailComposeViewControllerDelegate>

步骤3:添加以下发送电子邮件的方法。

 - (void) sendEmail {
 // Check if your app support the email.
 if ([MFMailComposeViewController canSendMail]) {
    // Create an object of mail composer.
    MFMailComposeViewController *mailComposer =      [[MFMailComposeViewController alloc] init];
    // Add delegate to your self.
    mailComposer.mailComposeDelegate = self;
    // Add recipients to mail if you do not want to add default recipient then remove below line.
    [mailComposer setToRecipients:@[<add here your recipient objects>]];
    // Write email subject.
    [mailComposer setSubject:@“<Your Subject Here>”];
    // Set your email body and if body contains HTML then Pass “YES” in isHTML.
    [mailComposer setMessageBody:@“<Your Message Body>” isHTML:NO];
    // Show your mail composer.
    [self presentViewController:mailComposer animated:YES completion:NULL];
 }
 else {
 // Here you can show toast to user about not support to sending email.
}
}

步骤4:实现MFMailComposeViewController Delegate

- (void)mailComposeController:(MFMailComposeViewController *)controller didFinishWithResult:(MFMailComposeResult)result error:(nullable NSError *)error {
[controller dismissViewControllerAnimated:TRUE completion:nil];


switch (result) {
   case MFMailComposeResultSaved: {
    // Add code on save mail to draft.
    break;
}
case MFMailComposeResultSent: {
    // Add code on sent a mail.
    break;
}
case MFMailComposeResultCancelled: {
    // Add code on cancel a mail.
    break;
}
case MFMailComposeResultFailed: {
    // Add code on failed to send a mail.
    break;
}
default:
    break;
}
}

我写了一个简单的包装器KRNSendEmail，它简化了发送电子邮件到一个方法调用。 KRNSendEmail被很好地记录并添加到CocoaPods中。 https://github.com/ulian-onua/KRNSendEmail