Hi if POP3 and MAPI clients are enabled in exchange 2003 organization . Can we find out which user is using POP3 client and which one MAPI client Is there any tool for the same Regards

It could be tedious, but you can review the IIS logs on the Exchange 2003 server as this will include POP3 connections. As far as MAPI connection, you can use the Excahnge User Monitor (http://www.msexchange.org/tutorials/microsoft-exchange-server-user-monitor.html) to track these users. This tool only tracks MAPI connections though, so IMAP users may still need to be pulled from the IIS logs.