Gateways exist in several forms.
They can be fully bi-directional between the list and the group, one way from the list to the group, or only partially passed from the group to the list and back, with the list moderator selecting articles which are appropriate. Traffic on mailing lists whose incoming traffic from the corresponding newsgroup is unrestricted is often very unlike that which comes to lists that solely exist in the mail realm. This is because of differences of the two overall environments and how they are used by people. Both list members and group participants should be wary of it and try to be sympathetic with the other side, but this is often a point missed by the group users who don't even realise their articles are being redistributed via an automatic gateway. As noted in that article, most modern news system software supports automatic submission to the moderator of articles posted to the group.