To cancel sending an email with Thunderbird, you need to act quickly before the email is actually sent. Here's what you can do:
Locate the "Outbox" folder in Thunderbird. This folder holds emails that are in the process of being sent.
Open the "Outbox" folder and find the email you want to cancel.
Drag the email back to the "Drafts" folder. By doing this, you're essentially moving the email back to the drafts section, allowing you to make any necessary changes or completely discard it.
If you wish to make changes to the email before sending it, double-click on the email in the "Drafts" folder to open it. Make the desired modifications and save the changes.
If you want to discard the email entirely, you can delete it from the "Drafts" folder.
By following these steps, you can effectively cancel the sending of an email in Thunderbird. However, keep in mind that if the email has already been sent or if it's sitting in the Outbox and Thunderbird is actively attempting to send it, you may not be able to stop it from being sent. In such cases, you could try disconnecting your computer from the internet quickly to prevent the email from being sent, but this method is not always reliable.