Sending an email from swift 3

first Add UIMessage Package from for Application then Write this Code and connect them at your Storyboard :

import UIKit

import MessageUI

class SendDropMailVC: UIViewController , MFMailComposeViewControllerDelegate {

    @IBOutlet weak var subject: UITextField!

    @IBOutlet weak var Body: UITextView!

    override func viewDidLoad() {

        super.viewDidLoad()

}

    override func didReceiveMemoryWarning() {

        super.didReceiveMemoryWarning()

}

    @IBAction func SendEmail(_ sender: AnyObject) {

        var SubjectText = "Your Subject:"

        SubjectText += subject.text!

        let messageBody = Body

        let toRecients = ["123@email.com"]

        let mc: MFMailComposeViewController = MFMailComposeViewController()

        mc.mailComposeDelegate = self

        mc.setSubject(SubjectText)

        mc.setMessageBody((messageBody?.text)!, isHTML: false)

        mc.setToRecipients(toRecients)

        self.present(mc, animated: true, completion: nil)

}

    func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {

        switch result.rawValue{

        case MFMailComposeResult.cancelled.rawValue:

            NSLog("Mail Cancelled")

        case MFMailComposeResult.saved.rawValue:

            NSLog("Mail Saved")

        case MFMailComposeResult.sent.rawValue:

            NSLog("Mail Sent")

        case MFMailComposeResult.failed.rawValue:

            NSLog("Mail Sent Failure: %@" , [error!.localizedDescription])

        default:

            break

}

        self.dismiss(animated: true, completion: nil)

}

Add a UITextField! & UITextView! to your view with a button as you see in the picture

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Swift Programing