Is it possible to enable a small email footer (2 or 3 lines of text) on all inbound & outbound mail ?

I'd like to be able to control this at a domain level (i.e. I don't want all my customers to get the message added) again if possible it would be good to be able to turn this off at a indvidual user level within the domain.

Any suggestions

I'm using a fairly default Cpanel/WHM 9.1