asp.net MVC mail sending fails sometimes - asp.net

Question

In my application, it sometimes fail to send mail and it is not domain specific (i.e. in gmail sometimes mail is sent and sometimes it is not as per client complain). What can be the reason, any idea? I m attaching the code of my identityConfig.cs
using System;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.EntityFramework;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.Owin;
using Microsoft.Owin.Security;
using RoasterManagementSystem.Data.DbContext;
using RoasterManagementSystem.Model;
using System.Net;
using System.Net.Mail;
namespace RoasterManagementSystem.App
{
public class EmailService : IIdentityMessageService
{
public async Task SendAsync(IdentityMessage message)
{
var smtpConfig = new System.Net.Mail.SmtpClient();
var credential = (System.Net.NetworkCredential)smtpConfig.Credentials;
var fromAddress = new MailAddress(credential.UserName, "Roster Management Application");
var toAddress = new MailAddress(message.Destination);
string fromPassword = "123456Tt";
string subject = message.Subject;
string body = message.Body;
var smtp = new SmtpClient
{
Host = smtpConfig.Host,
Port = smtpConfig.Port,
EnableSsl = smtpConfig.EnableSsl,
DeliveryMethod = SmtpDeliveryMethod.Network,
UseDefaultCredentials = smtpConfig.UseDefaultCredentials,
Credentials = new NetworkCredential(credential.UserName, credential.Password)
};
var mail = new MailMessage(fromAddress, toAddress)
{
Subject = subject,
Body = body,
IsBodyHtml = true
};
using(smtp)
using (mail)
{
try
{
await smtp.SendMailAsync(mail);
}
catch (Exception ex)
{
//If email sending failed then do nothing for now
}
}
}
}
public class SmsService : IIdentityMessageService
{
public Task SendAsync(IdentityMessage message)
{
// Plug in your SMS service here to send a text message.
return Task.FromResult(0);
}
}
// Configure the application user manager used in this application. UserManager is defined in ASP.NET Identity and is used by the application.
public class ApplicationUserManager : UserManager<ApplicationUser>
{
public ApplicationUserManager(IUserStore<ApplicationUser> store)
: base(store)
{
this.UserValidator = new UserValidator<ApplicationUser>(this)
{
AllowOnlyAlphanumericUserNames = false,
RequireUniqueEmail = true
};
// Configure validation logic for passwords
this.PasswordValidator = new PasswordValidator
{
RequiredLength = 8,
RequireNonLetterOrDigit = false,
RequireDigit = true,
RequireLowercase = true,
RequireUppercase = true,
};
// Configure user lockout defaults
this.UserLockoutEnabledByDefault = true;
this.DefaultAccountLockoutTimeSpan = TimeSpan.FromMinutes(5);
this.MaxFailedAccessAttemptsBeforeLockout = 5;
// Register two factor authentication providers. This application uses Phone and Emails as a step of receiving a code for verifying the user
// You can write your own provider and plug it in here.
this.RegisterTwoFactorProvider("Phone Code", new PhoneNumberTokenProvider<ApplicationUser>
{
MessageFormat = "Your security code is {0}"
});
this.RegisterTwoFactorProvider("Email Code", new EmailTokenProvider<ApplicationUser>
{
Subject = "Security Code",
BodyFormat = "Your security code is {0}"
});
this.EmailService = new EmailService();
this.SmsService = new SmsService();
var dataProtectionProvider = Startup.DataProtectionProvider;
if (dataProtectionProvider != null)
{
this.UserTokenProvider =
new DataProtectorTokenProvider<ApplicationUser>(dataProtectionProvider.Create("ASP.NET Identity"));
}
}
}
// Configure the application sign-in manager which is used in this application.
public class ApplicationSignInManager : SignInManager<ApplicationUser, string>
{
public ApplicationSignInManager(ApplicationUserManager userManager, IAuthenticationManager authenticationManager)
: base(userManager, authenticationManager)
{
}
public override Task<ClaimsIdentity> CreateUserIdentityAsync(ApplicationUser user)
{
return user.GenerateUserIdentityAsync((ApplicationUserManager) UserManager);
}
}
}