BPS and email syncing

Hi.

I'm using BPS with BB 8900. I was wondering, if I delete an email in my BB, it reflects the same in my PC and the same email gets deleted. However, if I delete the email in my PC or webmail, it does not delete the same email in my BB. If I mark an email as "read" in the PC, it does not reflect in the BB. Is that really how it's supposed to behave, or am I missing some configuration? What about BES same thing?

Thanks