send email from asp.net app

i configure all setting for send email using c# but when i execute than i get the following error
The requested address is not valid in its context 74.125.53.109:25

my code is

MailMessage mail = new MailMessage();
 mail.To.Add("to@gmail.com");
 mail.From = new MailAddress("from@gmail.com");
 mail.Subject = "Test Email";
 
 string Body = "<b>Welcome to CodeDigest.Com!!</b>";
 mail.Body = Body;
 mail.IsBodyHtml = true;
 
 SmtpClient smtp = new SmtpClient();
 smtp.Host = ConfigurationManager.AppSettings["SMTP"];
 smtp.Credentials = new System.Net.NetworkCredential(ConfigurationManager.AppSettings["FROMEMAIL"], ConfigurationManager.AppSettings["FROMPWD"]);
 smtp.EnableSsl = true;   
 smtp.Send(mail);
 

Web.Config

<appSettings>
 
     <add key="SMTP" value="smtp.gmail.com"/>
 
     <add key="FROMEMAIL" value="mail@gmail.com"/>
 
     <add key="FROMPWD" value="password"/>
 
   </appSettings>
 

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