Interesting question. When you walk up to a letter box and drop the mail into it. What happens if you go to the post office and ask for it back? People almost universally want an undo for their flame mails but the mail protocols do not have such an option.

Exchange and the other corporate e-mail systems are not e-mail per se. So, because they are essentially big databases of all the corporate mail they can undo the send unless the mail has been seen. This create an unrealistic expectation that it should be available in email, which it is not. Google delay the real send for several minutes to give you a cool down time and pretend this is a recall. In fact nothing has been done yet.

So, No there will be no unsend option in the foreseeable future in email. Not until Someone proposes such a change to the Internet Engineering TaskForce and their processes take years. You could choose to send your mail later by pressing Ctrl+Shit +Enter instead of the send button.

Longtimeusertip said

Need to be able to unsend email.

Referring to the new unsend feature that Google made available with its web-based Gmail.

Asking if the Thunderbird email client will have this?. Not likely.

I suppose a delay send could be a option in that it will then get sent after a time automatically or if you then manually confirm to indeed send it. At least then you have a chance to delete/cancel email.

Longtimeusertip said

Need to be able to unsend email.

I think a delay mechanism just like googles should be standard. This is major advance for people who work in information sensitive jobs like I have. Major but so simple that it should be standard.

then use the add-on. https://addons.mozilla.org/en-US/thunderbird/addon/blunderdelay/?src=ss

Or rather the Send Later extension. https://addons.mozilla.org/en-US/thunderbird/addon/send-later-3/