This question might be silly.

I was searching other's threads about sending mail from asp.net and have been looking tutorials but still can't send it.

The codes are

MailAddress To = new MailAddress("TowhereIwanttosend@somewhere.com");
        MailAddress From = new MailAddress(amazingsunday@sunday.com);
        MailMessage Mailer = new MailMessage(From, To);

        Mailer.Subject = "Testing";
        Mailer.Body = "Just Testing";
        SmtpClient Client = new SmtpClient();
        Client.Host = "localhost";

        Client.Send(Mailer);

        Response.Write("Successful sent");

And This is the error

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first i34sm4652534wxd

What is wrong with the code? Maybe I'm not understanding what i'm doing .Will be appreciate if you help.

Nothing is wrong w/ the code from what i can see

This error means that the SMTP server on the server housing IIS (localhost) is configured to require TLS encryption.  I am not sure what SMTP service you have installed on the server.  If it is IIS SMTP service, go to the SMTP service property -> Delivery -> Outbound Security and make sure TLS encryption is unchecked.

Hope this helps.

bluemistonline:

Is the SMTP service running on your computer? You need to install(its not by default) it to be able to send mail from your machine.

Yes,I guess It's running. I can see Default Virtual SMTP Server in IIS control Panel.

Yes,It's IIS SMTP service. It's already unchecked .

By the way the error is gone and it shown Response.write("Successful sent"); but I didn't receive any mail in my Inbox,

Do I need to do other stuff?

OK.. this means that the SMTP server (localhost) accepted the email, which is good news because this no longer is an issue with your asp.net code but a server side problem.

2 things to want to do to troubleshoot

a) Check the SMTP queue to see if the email is there. default location: c:\inetpub\mailroot\queue

b) Check the SMTP log to see why the email was not delivered.  Post the log if you have problem reading it.

There's no email in C:\Inetpub\mailroot\Queue folder,but in Badmail .

Sorry, I don't know where is the folder of smtp log .

if mail is in badmail folder, there some problem w/ the SMTP setup or the to address is bad.

Anyway, the default log file location is at c:\windows\system32\logfiles

Hi Bruce

SMTP service property -> Delivery -> Outbound Security and make sure TLS encryption is unchecked. 

Does  it applies to Gmail account too.Thanks

Sonia,

you lost me here.  What does this have to do w/ Gmail?

Hi!

I try to use smtp.gmail.com for passwordrecovery control and I get

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first f4sm7434685nfh...

I think I need to enable somewhere ssl (mailClient.EnableSsl = true;). Maybe in web.config?!

 Can somebody help me?

Found solution!

this works fine locally .. but when i tried hosting at http://www.vwdhosting.net i receive an error when sending mail! hope to find a solution