If you've found your way to this article, we know you can't be too happy at the moment. Unfortunately once a campaign has been sent, it cannot be stopped or edited. This includes the final send on A/B Split testing. Once the send button is clicked, we cannot stop the final send as the code has gone out to the servers and is waiting to be delivered based on your recipient's actions.
How about editing the archives?
The archived version of a sent campaign cannot be edited or updated in any way.
If you need to share a link to the campaign archive, we recommend replicating your campaign, making your edits, and sending it to yourself via a segment. Once the campaign has been sent to yourself, its archive link can be shared. If you host your own archive on your website, make sure to move the campaign out of your designated archive folder, and replace it with the new campaign.
Why is this so?
We serve content using a cloud computing environment. Once published, because of the infrastructure complexity, we can't go into the servers and make changes to campaigns that have already been pushed out for sending.
What can I do in the future?
It's best to make 100% sure you've done all your testing and proofing before you hit the send button. Recruit people to proof the campaign for you. Check every single link just to be sure they work. Once you hit the send button, there's absolutely no going back. We cannot even stop the campaign in the database.