Question on NET::SMTP new()

Hi folks
I am using NET::SMTP new() to connect to the SMTP server.I use the same
script to send mails.This script gets parameters to the new() as
new(smtp_server_name hello =>sender_domain) from various sources.
But for all the mails same smtp_server_name and sender_domain are being
used.
The problem is some times the mail goes successfully but for some mails
it says
bad file descriptor - smtp server not configured properly
for some it sends successfully
I do not know how to seggregate where the error lies
PLease help me on this.This is very urgent
Perl_programmer_sow