Outbox

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Thunderbird doesn't have a Outbox folder like Outlook Express. Sending messages and checking for new messages occur independently. However, it does have a Unsent folder that is used to queue messages to send later on. You can use the Send Later command to queue a message to the Unsent folder, and later on send them using either File -> Send Unsent Messages or by right clicking on the folder and selecting Send Unsent Messages. You can edit a message in the Unsent folder using "Message -> Edit Message As New".

At one time you needed to install an extension (or work offline) to use the Send Later command. However, recent versions of Thunderbird have a File -> Send Later command. Some of the extensions mentioned below also support a Send Later button.

Installing an extension that adds a button doesn't mean that you can actually see the button, it merely makes it available. Press the Write button, right click on the toolbar for the compose message window, drag and drop the button to the toolbar, and press OK.

The MagicSLR extension provides a combined "Get/Send" button. The BlunderDelay extension sends whatever messages are in the Unsent folder at regular intervals. The SendTools extension and the Send Later extension lets you schedule delivery times.

If you want to schedule a message to be sent while you are on a trip you need to keep Thunderbird running, and consider issues such as whether you should temporarily disable checking for new mail to avoid the possibility of downloading a new message with bad/missing headers causing a problem. One alternative would be to create a free account at the LetterMeLater web site and have it send the message instead.

Problems

Not all of the extensions support the latest version of Thunderbird. You may need to bypass the extensions version check per this article.

The Outbox extension is obsolete, doesn't support uninstalling and is not recommended.