I am from Chandigarh, India. I wrote a small program that sends mail. Our ISP's outgoing server is mail.satyam.net.in. If I treat it as my smtp server it gives me an error 553 but if I change the server to smtp.satyam.net.in it works but erratic at times mail I send is recd. in 10 seconds and some time times it takes upto 2 minutes.

What could be the problem?