Email not sending using SMTP in ASP.net - asp.net

Question

I am try to send email through SMTP in ASP.net but email not sending and not giving any error. My code:
//create the mail message
System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();
//set the FROM address
mail.From = new MailAddress("aaa#abc.com");
//set the RECIPIENTS
mail.To.Add("bbb#abc.com");
//enter a SUBJECT
mail.Subject = "Set the subject of the mail here.";
//Enter the message BODY
mail.Body = "Enter text for the e-mail here.";
//set the mail server (default should be smtp.1and1.com)
SmtpClient smtp = new SmtpClient("smtp.1and1.com");
//Enter your full e-mail address and password
smtp.Credentials = new NetworkCredential("example#abc.com", "xxxxxxx");
//send the message
smtp.Send(mail);
And my code in web.config is
<system.net>
<mailSettings>
<smtp deliveryMethod="SpecifiedPickupDirectory">
<specifiedPickupDirectory pickupDirectoryLocation="C:\Mail\" />
</smtp>
</mailSettings>
<defaultProxy enabled="true" />
</system.net>

Answer 1

Use breakpoint to display each parameter's value. Even if there is no error in the codes, parameter's value may be null or wrong. Before breakpoint, use try-catch as it below;
try
{
// Your codes
}
catch (Exception ex)
{
throw new Exception(ex.Message.ToString());
}

Answer 2

Check First you TLS Version.
Open your Site in IE(Internet Explorer) browser and go to page properties.
If your TLS 1.2 then Add below code before client.Send(Object);
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
like as per bellow
System.Net.Mail.SmtpClient objSMTPClient = new System.Net.Mail.SmtpClient();
SmtpClient client = new SmtpClient();
client.EnableSsl = true;
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
client.Send(oMail);
client.Dispose();
client = null;