How to delete all mails in mutt?
- In the main view press D (Shift + d)
- At the bottom it asks Delete messages matching:.
- Enter the following and press enter: ~s .*
All messages will now be marked for deletion. Just press q to quit and y to confirm you want to delete all messages.
The ~s makes it search the subject for the given expression and of course .* is a global regex wild card.