It's a New World Coming

I am trying to get my Palm Centro cell phone and the email messages on the computer lined up. Right now I have Mobile Email on the Palm which  downloads everything on the email accounts that I have set up there.  The question is "does that download delete the message from the online source so that I never get it in my pc?"  The Palm is a near instantaneous device.  Emails come down real time but talking to my pc on my home network is not clear cut yet.  It will come to me.