socket.gaierror: [Errno 11001] getaddrinfo failed

socket.gaierror: [Errno 11001] getaddrinfo failed

I have tried to attached a file to the mail using python. Code:
import smtplib
from email.MIMEMultipart import MIMEMultipart
from email.MIMEText import MIMEText
from smtplib import SMTPException
def send_Email():
file1="abc.txt"
message = "Request for new dump"
msg = MIMEMultipart()
msg.attach(MIMEText(file(file1).read()))
try:
smtpObj = smtplib.SMTP('smtp server name',port)
smtpObj.sendmail(sender, EmailId, message, msg.as_string() )
print "Successfully sent email"
except SMTPException:
print "Error: unable to send email"
Bt I have get the error: socket.gaierror: [Errno 11001] getaddrinfo failed