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C# SMTP MailMessage receiving error "5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM"

The code I currently have is:
public void SendEmail(string to, string cc, string bcc, string subject, string body, string attachmentPath = "", System.Net.Mail.MailPriority emailPriority = MailPriority.Normal, BodyType bodyType = BodyType.HTML)
{
try
{
var client = new System.Net.Mail.SmtpClient();
{
client.Host = "smtp-mail.outlook.com";
client.Port = 587;
client.UseDefaultCredentials = false;
client.EnableSsl = true;
client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
client.Credentials = new NetworkCredential("[my company email]", "[my password]");
client.Timeout = 600000;
}
MailMessage mail = new MailMessage("[insert my email here]", to);
mail.Subject = subject;
mail.Body = body;
client.Send(mail);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
The email address I'm trying to send to is hosted on Office 365's Outlook. We might have to change the specific address later, but they'd likely be configured the same.
However, whenever I try to run the client.Send(mail); command, I receive the same error. The full text of the error is:
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM
I've tried a few different things, like switching the port between 25 and 587, changing the host to Office365's, or toggling UseDefaultCredentials and EnableSssl to true or false. But I always see the same error. Is there something else I'm missing?

I found an example code block elsewhere on this site and replacing everything I had with it made the difference.
The function name and parameters were the same, but here's what I replaced the body of it with.
var _mailServer = new SmtpClient();
_mailServer.UseDefaultCredentials = false;
_mailServer.Credentials = new NetworkCredential("my email", "my password");
_mailServer.Host = "smtp.office365.com";
_mailServer.TargetName = "STARTTLS/smtp.office365.com";
_mailServer.Port = 587;
_mailServer.EnableSsl = true;
var eml = new MailMessage();
eml.Sender = new MailAddress("my email");
eml.From = eml.Sender;
eml.To.Add(new MailAddress(to));
eml.Subject = subject;
eml.IsBodyHtml = (bodyType == BodyType.HTML);
eml.Body = body;
_mailServer.Send(eml);
I don't know for certain but I think that replacing the Host value with the smtp Office 365 link rather than an outlook one, as well as remembering to add a Target Name which I did not have before, both did the trick and solved the authorization issue (I had previously confirmed it wasn't a credentials issue with our tech support).

smtp fails to send mail sometimes in c#

I have gone through some questions on this topic. All the answers relate when sending email fails all the time. In my case, it fails only sometimes with exception message:
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM...
If I try second time it works. I'm using the following configuration.
using (MailMessage mail = new MailMessage())
{
mail.From = new MailAddress("emailid", "displayname");
mail.To.Add("TOAddress");
mail.Subject = subject1;
mail.Body = body1;
mail.IsBodyHtml = true;
using (SmtpClient smtp = new SmtpClient("Outlook.office365.com", 587))
{
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential("emailid", "password");
smtp.EnableSsl = true;
smtp.Send(mail);
}
}
checked a similar question here , given solutions not working.

Try this(second answer): Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required
I used this code to send the email:
MailMessage msg = new MailMessage();
msg.From = new MailAddress("sender#gmail.com");
msg.To.Add("receiver#gmail");
msg.Subject = "Hello";
msg.Body = "Test";
SmtpClient smt = new SmtpClient();
smt.Host = "smtp.gmail.com";
System.Net.NetworkCredential ntcd = new NetworkCredential();
ntcd.UserName = "sender#gmail.com";
ntcd.Password = "senderPassword";
smt.Credentials = ntcd;
smt.EnableSsl = true;
smt.Port = 587;
smt.Send(msg);
Also check if your virus scanner doens't block your email from sending.

SMTP Mail with ASP.net Error 5.5.1 Authentication Required

Good day, I'm a beginner from using ASP.net and SMTP Mailer
Heres my Question, I always encounter this Error when i send email from my local
and searched and tried the solutions around the net but not so lucky,
I hope someone point out what codes do i need and where i encounter this errror
Message = "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"
Heres my Code:
protected void btnSendEmail_Click(object sender, EventArgs e)
{
// System.Web.Mail.SmtpMail.SmtpServer is obsolete in 2.0
// System.Net.Mail.SmtpClient is the alternate class for this in 2.0
SmtpClient smtpClient = new SmtpClient();
MailMessage message = new MailMessage();
try
{
MailAddress fromAddress = new MailAddress(txtEmail.Value, txtName.Value);
smtpClient.Credentials = new System.Net.NetworkCredential("myUser#gmail", "password");
// You can specify the host name or ipaddress of your server
// Default in IIS will be localhost
smtpClient.Host = "smtp.gmail.com";
smtpClient.EnableSsl = true;
//Default port will be 25
smtpClient.Port = 25;
smtpClient.UseDefaultCredentials = false;
//From address will be given as a MailAddress Object
message.From = fromAddress;
// To address collection of MailAddress
message.To.Add("myEmail#gmail.com");
message.Subject = txtSubject.Value;
// CC and BCC optional
// MailAddressCollection class is used to send the email to various users
// You can specify Address as new MailAddress("admin1#yoursite.com")
message.CC.Add("myEmail#gmail.com");
// You can specify Address directly as string
message.Bcc.Add(new MailAddress("myEmail#gmail.com"));
//Body can be Html or text format
//Specify true if it is html message
message.IsBodyHtml = false;
// Message body content
message.Body = txtaMessage.Value;
message.BodyEncoding = System.Text.Encoding.UTF8;
message.HeadersEncoding = System.Text.Encoding.UTF8;
// Send SMTP mail
smtpClient.Send(message);
lblSuccess.Text = "Email successfully sent.";
}
catch (Exception ex)
{
lblSuccess.Text = "Send Email Failed.";
}
}

i tried to make a simple codes for sending email try this
MailMessage mm = new MailMessage();
mm.From = new MailAddress("fromEmail");
mm.To.Add("toEmail");
mm.CC.Add("ccEmail");
mm.Subject = "StringSubject";
mm.Body = "BodySubject";
mm.IsBodyHtml = true;
SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com";
smtp.EnableSsl = true;
System.Net.NetworkCredential NetworkCred = new System.Net.NetworkCredential();
NetworkCred.UserName = "UsernameString";
NetworkCred.Password = "PasswordString";
smtp.UseDefaultCredentials = true;
smtp.Credentials = NetworkCred;
smtp.Port = 587;
try
{
smtp.Send(mm);
}
catch (Exception)
{
}

Try this reference ASP Simple SMTP for C# and VB it helps me a lot for may smtp problem

Please have a look on google support team, what they are saying regarding sending mail from application.
https://support.google.com/mail/answer/78775?hl=en
Also following link can help you.
Gmail Error :The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required

Goto Account of Gmail , then select
Connected apps & sites
Allow less secure apps: ON(if this is off you cannot send mails through apps,or your websites )

Problems sending e-mail in web app

I have been trying for 2 days to get my ASP.NET webforms application to send an e-mail.
I have tried this using both outlook and gmail. I got the smtp information for both from this tutorial:
When I try using port 587 in the example below I get an error saying:
An exception of type 'System.Net.Mail.SmtpException' occurred in System.dll but was not handled in user code
Additional information: The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.
When I try using port 465 in the example below:
My application just hangs forever and my page never gets back my email function which is in the PageLoad.
A couple of things to note just incase one of these is messing me up:
I am using a standard VS2013 dev environment (running my web app in debug mode using F5)
I am using the same e-mail address for from, to, and gmail login credentials)
My ISP does not block these ports. (comcast cable)
I even went to the google DisplayUnlockCaptcha page to Allow access to my account
protected void SendEmail()
{
string EmailAddress = "myemail#gmail.com";
using (MailMessage mailMessage = new MailMessage(EmailAddress, EmailAddress))
{
mailMessage.Subject = "This is a test email";
mailMessage.Body = "This is a test email. Please reply if you receive it.";
SmtpClient smtpClient = new SmtpClient();
smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpClient.EnableSsl = true;
smtpClient.Host = "smtp.gmail.com";
smtpClient.Port = 587;
smtpClient.Credentials = new System.Net.NetworkCredential()
{
UserName = EmailAddress,
Password = "password"
};
smtpClient.UseDefaultCredentials = false;
smtpClient.Send(mailMessage);
}
}

This code should work fine for you
protected void SendEmail()
{
string EmailAddress = "myemail#gmail.com";
MailMessage mailMessage = new MailMessage(EmailAddress, EmailAddress);
mailMessage.Subject = "This is a test email";
mailMessage.Body = "This is a test email. Please reply if you receive it.";
SmtpClient smtpClient = new SmtpClient();
smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpClient.EnableSsl = true;
smtpClient.Host = "smtp.gmail.com";
smtpClient.Port = 587;
smtpClient.Credentials = new System.Net.NetworkCredential()
{
UserName = EmailAddress,
Password = "password"
};
smtpClient.UseDefaultCredentials = false;
smtpClient.Send(mailMessage);
}
You'll need to set the delivery mode otherwise gmail will return an error
EDIT:
Throwing an 'using' around 'MailMessage' might also be a smart thing to do

It turns out that it is because of a GMail security setting.
https://www.google.com/settings/security/lesssecureapps
You have to enable access for less secure apps.

public void sendEmail(string body)
{
if (String.IsNullOrEmpty(email))
return;
try
{
MailMessage mail = new MailMessage();
mail.To.Add(email);
mail.To.Add("xxx#gmail.com");
mail.From = new MailAddress("yyy#gmail.com");
mail.Subject = "sub";
mail.Body = body;
mail.IsBodyHtml = true;
SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com"; //Or Your SMTP Server Address
smtp.Credentials = new System.Net.NetworkCredential
("yyy#gmail.com", "pw"); // ***use valid credentials***
smtp.Port = 587;
//Or your Smtp Email ID and Password
smtp.EnableSsl = true;
smtp.Send(mail);
}
catch (Exception ex)
{
print("Exception in sendEmail:" + ex.Message);
}
}``
http://www.c-sharpcorner.com/UploadFile/47548d/how-to-send-bulk-email-using-Asp-Net/

Time out Error in send mail

I use this code to try and send an email. After a few seconds, it shows me an error message claiming the operation has timed out. How can I resolve this issue?
try
{
MailAddress from = new MailAddress("from#yahoo.com", "name", Encoding.UTF8);
MailAddress to = new MailAddress("to#yahoo.com");
MailMessage message = new MailMessage(from, to);
message.Subject = "Test";
message.SubjectEncoding = Encoding.UTF8;
message.Body = "Test";
message.BodyEncoding = Encoding.UTF8;
SmtpClient client = new SmtpClient();
client.Host = "smtp.mail.yahoo.com";
client.Port = 465;
client.EnableSsl = true;
client.Credentials = new NetworkCredential("example#yahoo.com", "Password");
client.Send(message);
MessageBox.Show("sending Successfully!!!");
}
catch (SmtpException ex)
{
MessageBox.Show(ex.ToString());
}

Are you sure that you can reach smtp.mail.yahoo.com on port 465? Sounds pretty much like a network related issue. Generally when something times out, it means that it tries to connect to the server for a certain amount of time and them stops and gives you an error.
One easy way to test this is to telnet to smtp.mail.yahoo.com on port 465 and see if it times out. You can use Putty or the built in telnet-client in windows, if you have it installed.

As per my understanding, your code won't work because yahoo.com does not provide you access via SMTP. For that you need to upgrade to Yahoo! Mail Plus.
Couldn't find any sort of kb from Yahoo! on this. I got the information from a Yahoo! article on How to read Yahoo! Mail Plus using Outlook Express. The first two lines of the article are very relevant.
Do you want to read and send your Yahoo! email with Outlook Express?
If you are a Yahoo! Mail Plus user you can.
And also, the outgoing SMTP server should be
client.Host = "plus.smtp.mail.yahoo.com";

i had the same problem
you have to set the clietn.port as 25 and you have to specify your login an password in client.Credentials = new NetworkCredential(login,password)
when i did that i can send mail without problem
there is the code
{
SmtpClient client = new SmtpClient("188.125.69.59");//you can put the ip adress or the dns of smtp server (smtp.mail.yahoo.com as exemple)
// Specify the e-mail sender.
// Create a mailing address that includes a UTF8 character
// in the display name.
MailAddress from = new MailAddress("from#yahoo.fr");
// Set destinations for the e-mail message.
MailAddress to = new MailAddress("to#gmail.com");
// Specify the message content.
MailMessage message = new MailMessage(from, to);
message.Body = "This is a test e-mail message sent by an application. ";
// Include some non-ASCII characters in body and subject.
string someArrows = new string(new char[] {'\u2190', '\u2191', '\u2192', '\u2193'});
message.Body ="cc";
message.BodyEncoding = System.Text.Encoding.UTF8;
message.Subject = "test message 1";
message.SubjectEncoding = System.Text.Encoding.UTF8;
string userState = "test message1";
MessageBox.Show("sending");
client.Port = 25;
// client.Timeout = 40000;
client.ServicePoint.MaxIdleTime = 1;
client.Credentials = new System.Net.NetworkCredential("from#yahoo.fr", "pass");
//client.SendAsync(message, userState);
client.Send(message);
MessageBox.Show("Sending message... press c to cancel mail. Press any other key to exit.");
string answer = Console.ReadLine();
// If the user canceled the send, and mail hasn't been sent yet,
// then cancel the pending operation.
// if (answer.StartsWith("c") && mailSent == false)
//{
// client.SendAsyncCancel();
//}
// Clean up.
message.Dispose();
MessageBox.Show("Goodbye.");
}

Use following setting for domain #yahoo.co.in.
var smtp = new System.Net.Mail.SmtpClient();
{
smtp.Host ="smtp.mail.yahoo.co.in";
smtp.Port = 25;
smtp.EnableSsl = true;
smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
smtp.Timeout = 20000;
}