Sending mail SMTP works with Gmail but fails when I try to send it from my domain

Question

I'm trying to send mail using SMTPClient in C#.

Everything was fine when I was sending mail using my Gmail account using HOSTNAME: smtp.gmail.com and PORT NUMBER: 587.

Here is the code which I used:

MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com",587)
//mail 
mail.From = new MailAddress("[email protected]","myself");
mail.To.Add("[email protected]");
mail.Subject = "Test Mail C#";
mail.Body = "Hello";
mail.IsBodyHtml = true;
//smtpclient
SmtpServer.Port = 587;
SmtpServer.EnableSsl = true;
SmtpServer.Credentials = new  System.Net.NetworkCredential("[email protected]", "password");

Boolean MailSent=true;
try
{
    SmtpServer.Send(mail);
}
catch (SmtpException ex)
{
    MessageBox.Show(ex.Message);
    MailSent = false;
}
finally
{
    if (MailSent == true)

        MessageBox.Show("mail sent");
    else
        MessageBox.Show("Failed to send mail");
}

Here are the details provided by the hosting service provider:

Secure SSL/TLS Settings (Recommended)
Username: [email protected]
Password: Use the email account’s password.
Incoming Server: mocha7004.mochahost.com
IMAP Port: 993
POP3 Port: 995 Outgoing Server: mocha7004.mochahost.com
SMTP Port: 465
Authentication is required for IMAP, POP3, and SMTP.
Non-SSL Settings (This is NOT recommended.)
Username: [email protected]
Password: Use the email account’s password.
Incoming Server: mail.opastonline.com
IMAP Port: 143
POP3 Port: 110
Outgoing Server: mail.opastonline.com
SMTP Port: 25 --> When raised a ticket they also suggested me to use 2525 or 25
Authentication is required for IMAP, POP3, and SMTP.

But when I replace them using the details provided by my host provider, I am unable to push the mail.

It shows different error messages when I change port numbers (which I was given by the provider):

port 25: The remote certificate is invalid according to the validation procedure.
port 2525: Failure Sending Mail
port 465: Operation timed out

I cross checked every possible thing, but seems I am lost somewhere.

it shows different messege when i change port numbers (which i was given by the provider) port 25: The remote certificate is invalid according to the validation procedure. port 2525: Failure Sending Mail port465: Operation timed out — Anup Raj
Are you sure your domain (smtp.yourdomain.com) handles your email? If for example you use Google Apps or any other third party sw to handle your email, the smtp configuration may be different. — Rafael Leites Luchese

Nimesh khatri Nimesh khatri · Accepted Answer · 2016-05-14T05:33:26

Go to security settings at the followig link https://www.google.com/settings/security/lesssecureapps and enable less secure apps . So that you will be able to login from all apps.

Sending mail SMTP works with Gmail but fails when I try to send it from my domain

1 Answers