luci/applications/luci-app-email/root/usr/share/rpcd/acl.d/luci-app-email.json

{
	"luci-app-email": {
		"read": {
			"uci": [
				"emailrelay"
			]
		},
		"write": {
			"uci": [
				"emailrelay"
			]
		}
	}
}