Configure Thunderbird to send messages at a later time

You can do some pretty fancy things with this. For example, if you enter “now” in the text box and check that you only want the message to be delivered between 9:00am and 5:00pm Monday through Friday, and then save those as your defaults, then whenever you pop up the dialog, the default behavior will be to send the message now or reschedule it for when it is during business hours.

Keep in mind:

Whenever Send Later delivers a scheduled message, any other messages pending delivery in your Outbox will also be delivered.

Scheduled drafts are locked to a particular Thunderbird profile and will only be delivered by a Thunderbird running against the same profile that originally scheduled them.

This means that if you use Thunderbird on multiple computers to schedule messages, you need to keep it running on all of those computers for the messages to be delivered. You can “transfer” a draft from one profile to another if need be by editing and rescheduling it.