//
        // POST: /Account/ForgotPassword
        [HttpPost]
        [AllowAnonymous]
        [ValidateAntiForgeryToken]
        public async Task<JsonResult> ForgotPassword(ForgotPasswordViewModel model, bool CaptchaValid)
        {
            string mensaje = String.Empty;

            if (ModelState.IsValid)
            {
                if (!CaptchaValid)
                    mensaje = "ERROR: Captcha inválido.";
                else
                {
                    var user = await UserManager.FindByEmailAsync(model.Email);
                    if (user == null || !(await UserManager.IsEmailConfirmedAsync(user.Id)))
                    {
                        mensaje = "ERROR: La dirección de correo electrónico no está registrada.";
                    }
                    else
                    {
                        var provider = new DpapiDataProtectionProvider("WebAttendance");
                        UserManager.UserTokenProvider = new DataProtectorTokenProvider<ApplicationUser, string>(provider.Create("UserToken")) as IUserTokenProvider<ApplicationUser, string>;
                        string code = await UserManager.GeneratePasswordResetTokenAsync(user.Id);
                        var callbackUrl = Url.Action("ResetPassword", "Account", new { userId = user.Id, code = code }, protocol: Request.Url.Scheme);
                        await UserManager.SendEmailAsync(user.Id, "Reset Password", "Por favor, cambie su contraseña al hacer click <a href="" + callbackUrl + "">aquí</a>");
                        return Json("INFO: Se envió un mail a su cuenta de correo con instrucciones para cambiar su contraseña.");
                    }
                }
            }

            // If we got this far, something failed, redisplay form
            return Json(mensaje);
        }

<system.net>
    <mailSettings>
      <smtp from="info@xxx.com">
        <network host="mail.desytec.cl" password="xxxx" port="587" userName="yyy@xxx.cl"  enableSsl="false"/>
      </smtp>
    </mailSettings>
  </system.net>

public class EmailService : IIdentityMessageService {
    public Task SendAsync(IdentityMessage message) {
        // Plug in your email service here to send an email.
        return Task.FromResult(0);
    }
}

// code from https://stackoverflow.com/questions/40674457/how-to-configure-sender-email-credentials-for-asp-net-identity-usermanager-sende
public async Task SendAsync(IdentityMessage message) {
    // Plug in your email service here to send an email.
    SmtpClient client = new SmtpClient();
    await client.SendMailAsync("email from web.config here",
                                message.Destination,
                                message.Subject,
                                message.Body);
}