Develop Reference

How to send email from a C# program

I would like to add email functionality to a WinForm program I'm writing in C#. I have an Android app that has email functionality. What it does is set up the email but then lets the user choose the email program, etc. Once that is chosen the email body is completed. But it's up to the use to select what email app they want to use.
I would like to do the same in Windows but I don't see how. I have tried the following (based on other questions and responses here) :
_from = new MailAddress("my email address", "xxxx");
_to = new MailAddress("xxxx3333#gmail.com", "yyyy");
SmtpClient smtp = new SmtpClient("smtp.gmail.com");
smtp.UseDefaultCredentials = true;
smtp.Port = 587;
smtp.EnableSsl = true;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp msgMail = new MailMessage();
smtp.Body = text;
msgMail.Subject = "Subject";
msgMail.From = _from;
msgMail.To.Add(_to);
smtp.EnableSsl = true;
msgMail.Subject = _subject;
msgMail.Body = Text;
msgMail.IsBodyHtml = false;
try
{
mailClient.Send(msgMail);
}
catch (Exception ex)
{
string msg = "Exception caught in sending the email: " + ex.ToString();
showMessage(msg);
}
msgMail.Dispose();
But I get:
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.
With similar code in Android, my program just gets to an email form but lets the user decide what email add they will use.
Is there a way to do this in Windows?
There is an almost identical question and response here:
C# Windows Form Application - Send email using gmail smtp
And I think I've followed this but...doesn't work.

To directly answer your question - you probably haven't enabled less secure apps on the gmail account you are using.
Otherwise though, you could investigate the syntax of mailto if you want to let the user elect a mail client to use to send the email: https://www.labnol.org/internet/email/learn-mailto-syntax/6748/
From the link:
Send an email to Barack Obama with the subject “Congrats Obama” and some text in the body of the email message
<a href=”mailto:obama#whitehouse.gov?
subject=Congrats%20Obama&body=Enjoy%20your%20stay%0ARegards%20″>
This isn't directly related to C#/Windows - but I do know entering mailto:someone#somewhere.com at the Run prompt works:
Presumably then you could do something like: (untested)
Process.Run("mailto:someone#somewhere.com");

From the server response messages it looks like you have to provide login credentials before you are allowed to send.
Replace:
smtp.UseDefaultCredentials = true;
With:
smtp.Credentials = new System.Net.NetworkCredential("yourusername", "yourpassword");
This should do the trick.

You may have forgotten in your code to add the Host
Try to use this :
SmtpClient smtp = new SmtpClient();
smtp.UseDefaultCredentials = true;
smtp.Host = "SRVMAIL";

Error sending email via SMTP in C#, Does this still work in 2017?

Having researched the issue extensively especially applying recommendations from similar issues on stackoverflow, the below code still returns error ""System.Net.Mail.SmtpException: Syntax error, command unrecognized. The server response was: connection rejected at....""
try
{
var mail = new MailMessage();
mail.From = new MailAddress("demo77377#gmail.com");
mail.To.Add(new MailAddress("xxxxxxx#gmail.com"));
mail.Subject = "TEST";
mail.Body = "This is a test mail from C# program";
using (var smtp = new SmtpClient())
{
smtp.Credentials = new System.Net.NetworkCredential("demo77377#gmail.com", "AABBCCDDEE1!","gmail.com");
smtp.Host = "smtp.gmail.com";
smtp.Port = 587;
smtp.EnableSsl = true;
smtp.UseDefaultCredentials = false;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Timeout = 10000;
//
smtp.Send(mail);
Console.WriteLine("Message sent successfully");
Console.ReadLine();
}
}
catch (Exception e)
I have done everything possible
On Client> I have alternated smtp properties (permutation) etc
On Server> I have made gmail account less secure, I have disabled captcha etc
I observed that similar issues on stackoverflow were mostly dated over 3years ago and thus, is it possible that gmail no longer supports this SMTP method via C#, likewise has it been deprecated in favor of gmail API
Also, please find provided in code, original password supplied for the gmail account, in order to confirm if this issue is general or isolated to this gmail account
Thanks

This code is verified to work fine:
var fromAddress = new MailAddress("YOUREMAIL#gmail.com", "YOUREMAIL#gmail.com");
var toAddress = new MailAddress("YOUREMAIL#gmail.com", "YOUREMAIL#gmail.com");
const string fromPassword = "YOURPASSWORD";
const string subject = "YOUREMAIL#gmail.com";
const string body = "YOUREMAIL#gmail.com";
var smtp = new SmtpClient
{
Host = "smtp.gmail.com",
Port = 587,
EnableSsl = true,
DeliveryMethod = SmtpDeliveryMethod.Network,
UseDefaultCredentials = false,
Credentials = new NetworkCredential(fromAddress.Address, fromPassword),
Timeout = 20000
};
using (var message = new MailMessage(fromAddress, toAddress)
{
Subject = subject,
Body = body
})
{
smtp.Send(message);
}
I'm not comfortable including your personal details even though you have so I have removed them. Obviously replace the email and password with the correct details.

Finally got it working after switching from my hotel's wireless network to office network...type of network connection has a role to play in sending email via SMTP in C#

Only getting "no connection could be made because the target machine actively refused it" on certain computers

The program runs on multiple computers within the same network. The mail is sent through an internal server. When I try to send an email from SmtpClient, it works on some computers but on others it gives me:
"System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 10.1.0.74:25"
I've tried looking it up and a lot of answers talk about the firewall or the smtp server blocking requests. The problem is it only errors on certain computers, and I'm unsure what the firewall settings are supposed to be.
The code for sending the email is as follows:
public void SendMessage(string subject, string messageBody, string fromAddress, string toAddress)
{
MailMessage message = new MailMessage();
SmtpClient client = new SmtpClient("10.1.0.74", 25);
// Set the sender's address
message.From = new MailAddress(fromAddress);
// Allow multiple "To" addresses to be separated by a semi-colon
if (toAddress.Trim().Length > 0)
{
foreach (string addr in toAddress.Split(';'))
{
if (addr.Trim() != "")
message.To.Add(new MailAddress(addr));
}
}
// Set the subject and message body text
message.Subject = subject;
message.Body = messageBody;
message.IsBodyHtml = true;
// Set the SMTP server to be used to send the message
//client.Host = "smtp.gmail.com";
System.Net.NetworkCredential a = new System.Net.NetworkCredential("User", "Pass");
//client.EnableSsl = true;
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.UseDefaultCredentials = false;
client.Credentials = a;
// Send the e-mail message
client.Send(message);
}
Edit:
Pinged the IP from the computer that's not working, got the following.

Enable SSL in your client and try other ports:
client.EnableSsl = true;
client.Port = 587;
// or
client.Port = 465;
Also you can check the connection with cmd command:
telnet smtp.gmail.com 587
Successful response usually looks like:
220 mx.google.com ESMTP

Send mail works locally but not on server?

This code works locally, but when I upload it to my server on Godaddy, it does not send the e-mail. Any idea why it doesn't work on their server? What do I need to change?
try {
MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");
mail.From = new MailAddress("Myemail#gmail.com");
mail.To.Add("Myemail#gmail.com");
mail.Subject = "New sign up";
mail.Body = "New member";
SmtpServer.Port = 587;
SmtpServer.Credentials = new System.Net.NetworkCredential("Myemail#gmail.com", "**Mypass**");
SmtpServer.EnableSsl = true;
SmtpServer.Send(mail);
} catch(Exception ex) {
throw ex;
}

They may be blocking outgoing SMTP connections in order to prevent spammers from using their service to send spam. You should check what error messages you're getting and check your server host's policy.

There are a couple of things you need to do when sending from inside a site hosted from Godaddy. Use their relay server to send the message (this won't work from your dev machine, you'll have to test it live after you upload it). Here is the relay server info. Also make sure the "from" address is an email within the same domain. I usually use the same as the toAddress. See here for info on why this is necessary.
This is the code I'm using to send from a site inside Godaddy:
btnSend.Disabled = true;
const string serverHost = "relay-hosting.secureserver.net";
var msg = new MailMessage(toAddress, toAddress);
msg.ReplyTo = new MailAddress(emailFrom);
msg.Subject = subject;
msg.Body = emailBody;
msg.IsBodyHtml = false;
try
{
var smtp = new SmtpClient();
smtp.Host = serverHost;
smtp.Credentials = new System.Net.NetworkCredential("account", "password");
smtp.Send(msg);
}
catch (Exception e)
{
//Log the errors so that we can see them somewhere
}

You need to send your email via the godaddy smtp servers. I experienced the same issue with them before I think. I believe they give instructions of how to login via their FAQ.

If you have ssh access to the server, try to telnet smtp.google.com via 25 and 465 ports also. If you get a timeout, then you're likely firewalled from connecting to these ports outside a certain IP range.
Port 587 is for TLS. As you're using SSL, try port 465.

Send mail from C# code using lotuslive credentials?

I am trying to send mail from C# code using lotuslive smtp. But I have no success in sending the mail. everytime it says {"Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host."}.
My code is working fine for other email hosts like gmail and yahoo.
below is the code that I have used.
MailMessage message = new MailMessage();
message.From = new MailAddress("fromaddress");
message.To.Add(new MailAddress("toaddress"));
message.Subject = "Test";
message.Body = "test";
SmtpClient client = new SmtpClient("companyname-com-smtp.mail.lotuslive.com", 465);
client.UseDefaultCredentials = false;
NetworkCredential credential = new NetworkCredential("companycredentials", "password");
client.Credentials = credential;
client.EnableSsl = true;
try
{
client.Send(message);
}
catch(Exception ex)
{
}

Outgoing SSL SMTP Server: -smtp.mail.lotuslive.com (port: 465) Please
Note: Outgoing SMTP access for third party email clients is not
available for Trial accounts.
If it is trail account then may cause some problems.
MailClient = new SmtpClient();
MailClient.Host = "smtp.mail.lotuslive.com/your host address";
MailClient.DeliveryMethod = SmtpDeliveryMethod.Network;
MailClient.Credentials = new System.Net.NetworkCredential(username, password);
MailClient.EnableSsl = true;
MailClient.Port = 465;
If you do not have demo account then Check this link - How to configure client in Outlook 2003.
Check these outlook configure settings match to your code settings.
If all this stuff is not the issue then it may be problem at your mail server. Check these links for information:
An existing connection was forcibly closed by the remote host in SMTP client
System.Net.Mail with SSL to authenticate against port 465