I think it's a bad idea. Let the ones/colleagues close to you know. Go and have a drinks do. But a blank e-mail is just plain silly. If want details why, let me know.In my case, ppl are bound to know that I am leaving (depends on where you are in the company). But I still won't send a blank e-mail, but instead, will talk to ppl individually and wish them well. More class and more 'personal' like this.