Send Later Thunderbird Extension

Use this extension to send reminder emails to yourself or others. After you compose the email, instead of the regular Ctrl + Enter to drop it into cyberspace, use Ctrl + Shift + Enter to pull up the send later dialog box and tell Thunderbird when to mail the message down to the minute. Remember to leave Thunderbird open, otherwise the message will not be sent. This extension is compatible with the latest Thunderbird version.

Send Later from Lifehacker