Accounts not deleted properly

Hi

I am having problems after terminating an account within WHM.

If I terminate an account on the server, the email sent from other domains on that server do not get sent on to the account on a new server - They seem to be going to the server that the account was initially deleted on.

Confused, say I have my domain and clients domains hosted on the same server - If i terminate my domain and shift it to another server, my clients email does not reach me.

Where do i edit and get rid of the things that are being left behind by the account termination within WHM?

Thanks