Unfortunately once a campaign has been sent, it cannot be stopped or edited since the content has already been sent to the servers. This includes the final send on A/B Split testing.
Below, we'll give you some additional information on the finite nature of campaign sends and what you can do in the future to ensure your campaign content is in good shape when you hit the Send button.
Archived Campaign Content
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 We Can't Alter Sent Content
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 You Can 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.
While it won’t change what your subscribers see, you can rename sent campaigns in your MailChimp account.