darkrc/devilspie2/thunderbird.lua

local function opacity(value)
	os.execute(string.format(
		"xprop -id %s -f _NET_WM_WINDOW_OPACITY 32c -set _NET_WM_WINDOW_OPACITY 0x%xffffff",
		get_window_xid(), math.max(math.min(value, 255), 0)
	))
end

local function rep(n, value)
	if n>0 then return value, rep(n-1, value) end
end

local margin = { rep(4, 16) }
if get_application_name():find("Thunderbird$") then
	if get_window_type():find("NORMAL$") then
		set_window_workspace(get_workspace_count())
		unmaximize()
		set_window_fullscreen(true)
		maximize()
		opacity(230)
	end
end