the - send mail using imap c#

Sending email through Gmail SMTP server with C# (18)

For some reason neither the accepted answer nor any others work for me for "Sending email in .NET through Gmail". Why would they not work?

UPDATE: I have tried all the answers (accepted and otherwise) in the other question, but none of them work.

I would just like to know if it works for anyone else, otherwise Google may have changed something (which has happened before).

When I try the piece of code that uses SmtpDeliveryMethod.Network, I quickly receive an SmtpException on Send(message). The message is

The SMTP server requires a secure connection or the client was not authenticated.

The server response was:

5.5.1 Authentication Required. Learn more at" <-- seriously, it ends there.


This is a question that I asked a long time ago, and the accepted answer is code that I've used many, many times on different projects.

I've taken some of the ideas in this post and other EmailSender projects to create an EmailSender project at Codeplex. It's designed for testability and supports my favourite SMTP services such as GoDaddy and Gmail.

  1. First check your gmail account setting & turn On from "Access for less secure apps"

We strongly recommend that you use a secure app, like Gmail, to access your account. All apps made by Google meet these security standards. Using a less secure app, on the other hand, could leave your account vulnerable. Learn more.

  1. Set

    smtp.UseDefaultCredentials = false;


    smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);

@Andres Pompiglio: Yes that's right you must change your password at least once.. this codes works just fine:

//Satrt Send Email Function
public string SendMail(string toList, string from, string ccList,
    string subject, string body)

    MailMessage message = new MailMessage();
    SmtpClient smtpClient = new SmtpClient();
    string msg = string.Empty;
        MailAddress fromAddress = new MailAddress(from);
        message.From = fromAddress;
        if (ccList != null && ccList != string.Empty)
        message.Subject = subject;
        message.IsBodyHtml = true;
        message.Body = body;
        // We use gmail as our smtp client
        smtpClient.Host = "";   
        smtpClient.Port = 587;
        smtpClient.EnableSsl = true;
        smtpClient.UseDefaultCredentials = true;
        smtpClient.Credentials = new System.Net.NetworkCredential(
            "Your Gmail User Name", "Your Gmail Password");

        msg = "Successful<BR>";
    catch (Exception ex)
        msg = ex.Message;
    return msg;
//End Send Email Function

AND you can make a call to the function by using:

Response.Write(SendMail(recipient Address, "[email protected]", "ccList if any", "subject", "body"))

CVertex, make sure to review your code, and, if that doesn't reveal anything, post it. I was just enabling this on a test ASP.NET site I was working on, and it works.

Actually, at some point I had an issue on my code. I didn't spot it until I had a simpler version on a console program and saw it was working (no change on the Gmail side as you were worried about). The below code works just like the samples you referred to:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Mail;
using System.Net;

namespace ConsoleApplication2
    class Program
        static void Main(string[] args)
            var client = new SmtpClient("", 587)
                Credentials = new NetworkCredential("[email protected]", "mypwd"),
                EnableSsl = true
            client.Send("[email protected]", "[email protected]", "test", "testbody");

I also got it working using a combination of web.config, and code (because there is no matching EnableSsl in the configuration file :( ).

Change your gmail password and try again, it should work after that.

Don't know why, but every time you change your hosting you have to change your password.

I had also try to many solution but make some changes it will work

host =
port = 587
username = [email protected]
password = password
enabledssl = true

with smtpclient above parameters are work in gmail

I had the same problem, but it turned out to be my virus protection was blocking outgoing "spam" email. Turning this off allowed me to use port 587 to send SMTP email via GMail

I ran into this same error ( "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at" ) and found out that I was using the wrong password. I fixed the login credentials, and it sent correctly.

I know this is late, but maybe this will help someone else.

I was getting the same error and none of the above solutions helped.

My problem was that I was running the code from a remote server, which had never been used to log into the gmail account.

I opened a browser on the remote server and logged into gmail from there. It asked a security question to verify it was me since this was a new location. After doing the security check I was able to authenticate through code.

I'm not sure which .NET version is required for this because eglasius mentioned there is no matching enableSsl setting (I'm using .NET 4.0, but I suspect it to work in .NET 2.0 or later), but this configuration justed worked for me (and doesn't require you to use any programmatic configuration):

    <smtp from="[email protected]" deliveryMethod="Network">
      <network defaultCredentials="false" enableSsl="true" host="" port="587" password="password" userName="[email protected]"/>

You might have to enable POP or IMAP on your Gmail account first:

I recommend trying it with a normal mail client first...

I've had some problems sending emails from my gmail account too, which were due to several of the aforementioned situations. Here's a summary of how I got it working, and keeping it flexible at the same time:

  • First of all setup your GMail account:
    • Enable IMAP and assert the right maximum number of messages (you can do so here)
    • Make sure your password is at least 7 characters and is strong (according to Google)
    • Make sure you don't have to enter a captcha code first. You can do so by sending a test email from your browser.
  • Make changes in web.config (or app.config, I haven't tried that yet but I assume it's just as easy to make it work in a windows application):
        <add key="EnableSSLOnMail" value="True"/>   

    <!-- other settings --> 


    <!-- settings -->
            <smtp from="[email protected]" deliveryMethod="Network">
                    userName="[email protected]"
                <!-- When using .Net 4.0 (or later) add attribute: enableSsl="true" and you're all set-->
Add a Class to your project:

Imports System.Net.Mail

Public Class SSLMail

    Public Shared Sub SendMail(ByVal e As System.Web.UI.WebControls.MailMessageEventArgs)


        'Since the message is sent here, set cancel=true so the original SmtpClient will not try to send the message too:
        e.Cancel = True

    End Sub

    Public Shared Sub SendMail(ByVal Msg As MailMessage)
    End Sub

    Public Shared Function GetSmtpClient() As SmtpClient

        Dim smtp As New Net.Mail.SmtpClient
        'Read EnableSSL setting from web.config
        smtp.EnableSsl = CBool(ConfigurationManager.AppSettings("EnableSSLOnMail"))
        Return smtp
    End Function

End Class

And now whenever you want to send emails all you need to do is call SSLMail.SendMail:

e.g. in a Page with a PasswordRecovery control:

Partial Class RecoverPassword
Inherits System.Web.UI.Page

Protected Sub RecoverPwd_SendingMail(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.MailMessageEventArgs) Handles RecoverPwd.SendingMail
    e.Message.Bcc.Add("[email protected]")
End Sub

End Class

Or anywhere in your code you can call:

SSLMail.SendMail(New system.Net.Mail.MailMessage("[email protected]","[email protected]", "Subject", "Body"})

I hope this helps anyone who runs into this post! (I used VB.NET but I think it's trivial to convert it to any .NET language.)

In addition to the other troubleshooting steps above, I would also like to add that if you have enabled two-factor authentication (also known as two-step verification) on your GMail account, you must generate an application-specific password and use that newly generated password to authenticate via SMTP.

To create one, visit: and choose Authorizing applications & sites to generate the password.

Oh...It's amazing... First I Couldn't send an email for any reasons. But after I changed the sequence of these two lines as below, it works perfectly.

client.UseDefaultCredentials = true;
client.Credentials = new System.Net.NetworkCredential("[email protected]", "password");

Hope this help!!! :)


I got the exact same error, it turns out Google's new password strengh measuring algorithm has changed deeming my current password as too weak, and not telling me a thing about it (not even a message or warning)... How did I discover this? Well, I chose to change my password to see if it would help (tried everything else to no avail) and when I changed my password, it worked!

Then, for an experiment, I tried changing my password back to my previous password to see what would happen, and Gmail didn't actually allow me to do this, citing the reason "sorry we cannot allow you to save this change as your chosen password is too weak" and wouldn't let me go back to my old password. I figured from this that it was erroring out because either a) you need to change your password once every x amount of months or b). as I said before, their password strength algorithms changed and therefore the weak password i had was not accepted, even though they did not say anything about this when trying to login ANYWHERE! This (number 2) is the most likely scenario, as my weak password was about 4 months old, and it let me use it in Gmail.

It's pretty bad that they said nothing about this, but it makes sense. Because most hijacked emails are logged into using software outside of gmail, and I'm guessing you are required to have a stronger password if you want to use Gmail outside of the Gmail environment.

I hope this helps!

Yet another possible solution for you. I was having similar problems connecting to gmail via IMAP. After trying all the solutions that I came across that you will read about here and elsewhere on SO (eg. enable IMAP, enable less secure access to your mail, using and so on), I actually set up a new gmail account once more.

In my original test, the first gmail account I had created, I had connected to my main gmail account. This resulted in erratic behaviour where the wrong account was being referenced by google. For example, running opened up my main account rather than the one I had created for the purpose.

So when I created a new account and did not connect it to my main account, after following all the appropriate steps as above, I found that it worked fine!

I haven't yet confirmed this (ie. reproduced), but it apparently did it for me...hope it helps.

  smtp.Host = ""; //host name
    smtp.Port = 587; //port number
    smtp.EnableSsl = true; //whether your smtp server requires SSL
    smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
    smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
    smtp.Timeout = 20000;

Dim SMTPClientObj As New Net.Mail.SmtpClient
SMTPClientObj.UseDefaultCredentials = False
SMTPClientObj.Credentials = New System.Net.NetworkCredential("[email protected]", "mypwd")
SMTPClientObj.Host = ""
SMTPClientObj.Port = 587
SMTPClientObj.EnableSsl = True
SMTPClientObj.Send("[email protected]","[email protected]","test","testbody")

If you get an error like "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at" as I get before this, make sure the line SMTPClientObj.UseDefaultCredentials = False included and this line should before the SMTPClientObj.Credentials.

I did try to switch these 2 lines the opposite way and the 5.5.1 Authentication Required error returned.