Attachements in Outlook not responding

Hi,
I am not able to attach files in the emails. I have Ms office 2003 in my system. Normally, I regularly use Outlook to send and receive emails. When I am attaching files and click on the send and receive buttons, it shows the mail is going but taking a very long time. I need to cancel it and start it again. Again it taking a long time. The size of attachment is around 1.3 mb. It is not a big size. But the mail is working when i send a email without the attachment. Why this so. Help.