Issue if email attachment is above 100 kb (asp.net)

hi,

 I face problem sending email attachment above 100kb as a standard windows user from an asp.net application, the messages are sent but the attachments are empty.

If the size of attachment is below 100kb it works fine. 

I have increased the message size of smtp virtual server IIS  to 2097152 kb i.e., 2 mb, but still the problem persists