Microsoft has quietly implemented a policy blocking employee emails containing the words “Palestine,” “Gaza,” or “genocide” on its internal Exchange servers, according to No Azure for Apartheid, a group of pro-Palestine Microsoft employees. The automated filter, which silently prevents such emails from reaching recipients was first detected on Wednesday—just after Microsoft’s Build developer conference faced repeated disruptions by the activist group.

Microsoft has been rocked by internal dissent over its collaboration with the Israeli military and government amid the ongoing assault on Gaza. The company has faced disruptions to its events, including protests from employees over its provision of cloud services and other critical infrastructure used by the Israeli military.

Now, the company appears to be tightening its grip on internal discourse. The terms “Israel” and “P4lestine” do not trigger a block, the group said. Microsoft did not immediately respond to a request for comment.