I want to write a code that may automatically mail my specific users.The mails are to be sent at a gap of 3 days,starting from the day my application begins.How to [u]execute the file automatically </u>that contains the queries and CDONTS code [u]on these specific days.</u>

You can use SQL Server, or IIS and do a drop to the pickup folder and then make the mail ap (SQL Server or IIS) pickup every so often. You should check out Microsoft's Technet stuff on <a href="http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/proddocs/entserver/qss_mail_setup.asp"> SMTP </a> and also some sample codes:
http://www.aspnetemail.com/help/welcome/queue_ms.html
http://drs.yahoo.com/S=2766679/K=spe...es/Q324037.doc

Hope that helps, I was just doing this a few days ago.