Where an email message goes after you send it but before the list owner approves it or before the list server gets around to sending it. Some list software allows you to queue a message and then set a time to send it automatically, either during a quiet period on the server or at a time when human approval isn’t available.

The 3 Things To Avoid When Emailing Your List
When you decide to have an opt-in list, it is not just a matter of sending your subscribers your promotional newsletters or catalogs.