Develop Reference

send an email using SMTP without password in C#

I have a web application using ASP.net and C#,in one step it will need
from the user to
send an email to someone with an attachments.
my problem is when the user will send the email i don't want to put their
password every time the user send.
i want to send an email without the password of the sender.
any way to do that using SMTP ?
and this is a sample of my code "not all".
the code is worked correctly when i put my password , but without it ,it
is not work, i need a way to send emails without put the password but
in the same time using smtp protocol.
private void button1_Click(object sender, EventArgs e)
{
string smtpAddress = "smtp.office365.com";
int portNumber = 587;
bool enableSSL = true;
string emailFrom = "my email";
string password = "******";
string emailTo = "receiver mail";
string subject = "Hello";
string body = "Hello, I'm just writing this to say Hi!";
using (MailMessage mail = new MailMessage())
{
mail.From = new MailAddress(emailFrom);
mail.To.Add(emailTo);
mail.Subject = subject;
mail.Body = body;
mail.IsBodyHtml = true;
// Can set to false, if you are sending pure text.
// mail.Attachments.Add(new Attachment("C:\\SomeFile.txt"));
// mail.Attachments.Add(new Attachment("C:\\SomeZip.zip"));
using (SmtpClient smtp = new SmtpClient(smtpAddress,portNumber))
{
smtp.UseDefaultCredentials = true;
smtp.Credentials = new NetworkCredential(emailFrom, password);
smtp.EnableSsl = enableSSL;
smtp.Send(mail);
}
MessageBox.Show("message sent");
}
}

I believe this can be accomplished easily, but with some restrictions.
Have a look at the MSDN article on configuring SMTP in your config file.
If your SMTP server allows it, your email object's from address may not need to be the same as the credentials used to connect to the SMTP server.
So, set the from address of your email object as you already are:
mail.From = new MailAddress(emailFrom);
But, configure your smtp connection one of two ways:
Set your app to run under an account that has permission to access the SMTP server
Include credentials for the SMTP server in your config, like this.
Then, just do something like this:
using (SmtpClient smtp = new SmtpClient())
{
smtp.Send(mail);
}
Let the configuration file handle setting up SMTP for you. This is also great because you don't need to change any of your code if you switch servers.
Just remember to be careful with any sensitive settings in your config file! (AKA, don't check them into a public github repo)

authentication error in sending mail from yahoo in c# windows application

i am trying to send email from my software using the smtp of yahoo but it shows the following error
"The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Authentication required".
I know about the less secure apps setting in google but i don't know about the settings in yahoo. the same code runs fine with the gmail account credentials. here is the code for reference.
string EmailFrom = "test#yahoo.com";
string EmailTo = "test#gmail.com";
string PassWord = "test123";
string EmailHost = "smtp.mail.yahoo.com";
string status = "";
string Body = "";
MailMessage message = new MailMessage();
SmtpClient smtp = new SmtpClient();
message.From = new MailAddress(EmailFrom);
message.To.Add(new MailAddress(EmailTo));
message.Subject = "Auto Backup at test" ;
message.Body = "Backup has been taken at test on" + DateTime.Now;
Body = "Backup has been taken at test on" + DateTime.Now;
smtp.Port = 587;
smtp.Host = EmailHost;
smtp.EnableSsl = true;
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential(EmailFrom, PassWord);
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
//ServiceLogLibrary.WriteErrorlog("Step:5");
//Library.WriteErrorlog("Before sending mail");
smtp.Send(message);

Just providing some more information here as things have changed a little since the accepted answer was posted.
Go to the account security settings (https://login.yahoo.com/account/security)
Scroll to the bottom and search for the "Manage app passwords" heading as shown below and click it to add a new app.
Select an app type and generate the password. For API apps, use "Other App".
Use this password instead of your standard mailbox password when sending emails via your SmtpClient.

You need to go to
Go to your "Account security" settings.
Select Allow apps that use less secure sign in.
To deny or turn off app access, deselect the undesired app.
Source:Temporarily allow or deny access to apps using older security sign in

using gmail as smpt for deliver email from mvc controller

I'm trying to send email from asp.net mvc controller. Gmail account used here for smpt is configured to use with less security, so that's not the problem here.
but I don't get any error message neither any exception, but it not
deliver at my expected email address.
I'm using code
var text = "email body to deliver";
SendEmail("mydeliverEmailAddress#gmail.com", text);
public static bool SendEmail(string SentTo, string Text)
{
SmtpClient client = new SmtpClient();
client.Credentials = new NetworkCredential("myemail#gmail.com", "myGmailPass");
client.Port = 465;
client.Host = "smtp.gmail.com";
client.EnableSsl = true;
try
{
MailAddress
maFrom = new MailAddress("sender_email#domain.tld", "Sender's Name", Encoding.UTF8),
maTo = new MailAddress(SentTo, "Recipient's Name", Encoding.UTF8);
MailMessage mmsg = new MailMessage(maFrom.Address, maTo.Address);
mmsg.Body = "<html><body><h1>Some HTML Text for Test as BODY</h1></body></html>";
mmsg.IsBodyHtml = true;
mmsg.Subject = "Some Other Text as Subject";
mmsg.SubjectEncoding = Encoding.UTF8;
client.Send(mmsg);
}
catch (Exception ex)
{
}
return true;
}

Wait a minute. You are using your gmail account: myemail#gmail.com and trying to send an email on behalf of sender_email#domain.tld?
For more than obvious reasons that's never gonna work. So make sure that you are using the same email address as the one you are authenticating against:
maFrom = new MailAddress("myemail#gmail.com", "Sender's Name", Encoding.UTF8),
You can only send emails from the account you are authenticated against. Of course the recipient email can be any address that gmail can deliver to.
You've got another issue with your code. You are using a wring port here:
client.Port = 465;
The correct port that gmail SMTP works with is the following:
client.Port = 587;
Also you might want to ensure that you have enabled less secure apps in your gmail account or you will not be able to use SmtpClient in .NET to send emails using this SMTP: https://www.google.com/settings/security/lesssecureapps?pli=1
but I don't get any error message neither any exception, but it not
deliver at my expected email address.
What error message do you expect to get when you did the worst ever possible thing? You wrapped your code in a try/catch block and in your catch block you did absolutely nothing. You just consumed the exception:
catch (Exception ex)
{
}
So make sure that you do something useful with an exception if you are going to be catching it. For example something useful could be to log this exception and send an error message to the user saying that something bad happened and you couldn't send an email and that you are investigating the issue right now.

var smtpClient = new SmtpClient("YourSMTPServer", "SMTPServerPort"))
{
Credentials = new NetworkCredential("YourEmail",
"Password"),
EnableSsl = false
};
string fromEmail = "YourEmail";
var mailMessage = new MailMessage();
mailMessage.From = new MailAddress(fromEmail);
mailMessage.To.Add("Recipient's EMail");
mailMessage.Subject = "Test Mail";
mailMessage.Body = "This is test Mail";
mailMessage.IsBodyHtml = true;
smtpClient.Send(mailMessage);

How do I send an email with Gmail and SmtpClient when the sending account uses two factor authentication?

SmtpClient smtpClient = new SmtpClient();
NetworkCredential basicCredential =
new NetworkCredential("sender#gmail.com", "password");
MailMessage message = new MailMessage();
MailAddress fromAddress = new MailAddress("sender#gmail.com");
smtpClient.EnableSsl = true;
smtpClient.Host = "smtp.gmail.com";
smtpClient.Port = 587;
smtpClient.UseDefaultCredentials = false;
smtpClient.Credentials = basicCredential;
message.From = fromAddress;
message.Subject = "your subject";
//Set IsBodyHtml to true means you can send HTML email.
message.IsBodyHtml = true;
message.Body = "<h1>Hello, this is a demo ... ..</h1>";
message.To.Add("receiver#gmail.com");
try
{
smtpClient.Send(message);
}
catch (Exception ex)
{
//Error, could not send the message
ex.ToString();
}
// The thing is that this code works fine for gmails without phone number protection. Exception occurs when using this code with gmails that are protected(verified) via the client phone number.
One of the solution is to use a remote server to access clients mails.
Now my question is there another method to solve this issue ? other than third parties.

If I understand you correctly, you're saying the Google account is using two-factor authentication.
If that's the case, you need to create an Application Password for this. Go to https://security.google.com/settings/security/apppasswords once logged in as the account you want to two-factor auth with.
In the list, under Select App choose "Other" and give it some name. Click Generate, and write this password DOWN cause you will only ever see it ONCE. You will use this in your authentication. It will be 16-characters long and the spaces don't matter, you can include them or omit them. I included them here just because.
NetworkCredential basicCredential =
new NetworkCredential("sender#gmail.com", "cadf afal rqcf cafo");
MailMessage message = new MailMessage();

Hmailserver C# SMTP

I'm just trying to get my hmailserver to send mail from my C# program. The part that's killing me is the SSL part.
I originally got this error: The SMTP server requires a secure connection or the client was not authenticated. The server response was: SMTP authentication is required.
So I added: smtp.EnableSsl = true; and now I get Server does not support secure connections.
Here is my code, this is driving me nuts. Do I have to create my own SSL or is there a way to disable SSL on hmailserver side?
MailMessage mail = new MailMessage("jlnt#ademo.net", "com", "NEW Item", emailBody);
SmtpClient smtp = new SmtpClient("1.1.1.250");
smtp.Port = 25;
NetworkCredential login = new NetworkCredential("ja#test.net", "dg");
smtp.Credentials = login;
smtp.EnableSsl = true;
smtp.UseDefaultCredentials = false;
smtp.Send(mail);

Ahh okay what you have to do is in HMailServer go to advanced- ip ranges. Create a new IP range for example if you 192.168.1.2, you have to make the range 192.168.1.1-192.168.1.3, then at bottom uncheck all the required smtp authentication boxes.
Annoying...

To enable secure connection to send email throught your email provider, you have to change the port number.
MailMessage mail = new MailMessage("jlnt#ademo.net", "com", "NEW Item", emailBody);
SmtpClient smtp = new SmtpClient("1.1.1.250");
//smtp.Port =25;
smtp.Port =587;
NetworkCredential login = new NetworkCredential("ja#test.net", "dg");
smtp.Credentials = login;
smtp.EnableSsl = true;
smtp.UseDefaultCredentials = false;
smtp.Send(mail);

i was having this issue, what i did was used localhost ip and EnableSsl to false
SmtpClient smtpClient = new SmtpClient();
smtpClient.Host = "127.0.0.1";
smtpClient.Credentials = new NetworkCredential("test#123test.com", "pass123");
smtpClient.EnableSsl = false;
// then your other statements like: from, to, body, to send mail
this guide will help you setup custom NetworkCredentials in HMailServer as used above, hope helps someone.

I have stumbled on this question when trying to configure hMailServer to work to e-mail sending from C#. I have tried the following:
C# SmtpClient - does not work with implicit SSL - see this question and answers
AegisImplicitMail from here - could not make it work with UTF-8 strings (I have diacritics in my strings)
MailKit from here - very powerful and mature, no problems using it
I aimed for the following:
decent security
being able to send e-mails to mainstream e-mail providers (e.g. Google, Yahoo) and reach Inbox
being able to receive e-mails from mainstream e-mail providers
C# code
public void MailKitSend(string senderEmail, string senderName, string subject, string bodyText, string receivers, string receiversCc)
{
// no receivers, no e-mail is sent
if (string.IsNullOrEmpty(receivers))
return;
var msg = new MimeMessage();
msg.From.Add(new MailboxAddress(Encoding.UTF8, senderName, senderEmail));
msg.Subject = subject;
var bb = new BodyBuilder {HtmlBody = bodyText};
msg.Body = bb.ToMessageBody();
IList<string> receiversEmails = receivers.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries).ToList();
foreach (string receiver in receiversEmails)
msg.To.Add(new MailboxAddress(Encoding.UTF8, "", receiver));
if (!string.IsNullOrEmpty(receiversCc))
{
IList<string> receiversEmailsCc = receiversCc.Split(new[] { ";" }, StringSplitOptions.RemoveEmptyEntries).ToList();
foreach (string receiverCc in receiversEmailsCc)
msg.Cc.Add(new MailboxAddress(Encoding.UTF8, "", receiverCc));
}
try
{
var sc = new MailKit.Net.Smtp.SmtpClient();
if (!string.IsNullOrWhiteSpace(SmtpUser) && !string.IsNullOrWhiteSpace(SmtpPassword))
{
sc.Connect(SmtpServer, 465);
sc.Authenticate(SmtpUser, SmtpPassword);
}
sc.Send(msg);
sc.Disconnect(true);
}
catch (Exception exc)
{
string err = $"Error sending e-mail from {senderEmail} ({senderName}) to {receivers}: {exc}";
throw new ApplicationException(err);
}
}
hMailServer configuration
1) Opened ports - 25, 143, 465, 995 are opened to ensure that you can send and receive e-mail
2) TCP/IP ports configuration
SMTP / 0.0.0.0 / port 25 / no security (allow receiving start process)
SMTP / 0.0.0.0 / port 465 / SSL/TLS security (must define a SSL certificate)
POP3 / 0.0.0.0 / port 995 / SSL/TLS security (use the same SSL certificate)
3) pre C# testing
Run Diagnostics from hMailServer Administrator
Use an e-mail client that allows manual configuration of various settings such as ports for each protocol, security. I have used Thunderbird. Include sending of e-mails to external providers and receiving e-mails from them (I have tried with Gmail).
I made no changes in IP ranges and left the implicit ones (My computer and the Internet).

Although it's 7 years passed since the accepted answer was posted - I also upvoted it in the beginning - I want to emphasize that the suggested solution disables the whole authentication process which is unnecessary. The problem is the line with :
smtp.UseDefaultCredentials = false;
Just remove that line and it should work.
I post here the working solution for me (note that I'm not using SSL):
MailMessage mail = new MailMessage("a1#test.com", "foooo#gmail.com");
SmtpClient client = new SmtpClient();
client.Credentials = new NetworkCredential("a1#test.com", "test");
client.Port = 25;
client.EnableSsl = false;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Host = "...IPv4 Address from ipconfig...";
mail.Subject = "this is a test email.";
mail.Body = "this is my test email body";
client.Send(mail);