I don't usually let my email reader send out email receipts. If you have sent an email to me expecting to get a read- or a return-receipt, please don't. I don't mean to be rude. I simply don't like them. They're broken in several ways: they aren't reliable and they can be misused. So, why bother?
If you want to know if and when I read your email, please, say so. A simple "Please, acknowlege this." at the end of the message will trigger an instant reply. But please, don't make it a part of your signature. Not every message needs an acknowlegement and if you always require them I'll soon start to avoid replying. Few things annoy me more than a signature with a "I look forward to your reply" (or an equivalent "Aguardo retorno" in Portuguese) in it. I think that's rude.
