Problem with My Application communicating with my MS Exchange Server

Hi ,
I have a problem. I have made an application using Sockets. I want to connect to MS Exchange Server on another system within my network. I
have put the RemoteHost as "computername1" and remoteport as 110.
Now initially when I connect to that port , my application retrieves the data from MS Exchange as "+OK Microsoft Exchange POP3 server version 5.0.1457.10 ready" from the DataArrival Event within my application.
Now when I send the next data through the method SendData as "user username1" there is no response back. That is the Data Arrival Event doesnt fire . Why is this so. This is the case with any SMTP protocol that I send to the Exchange Server. But all these POP3 commands work fine when I use telnet.
Could anyone help me out. Thanks in Advance.

Saju