One easy solution to this (and many other general email mishaps) is to enable Gmail's undo button for sending email: https://support.google.com/mail/answer/1284885?hl=en
Now that I reread it and some of the responses, I think he's just arguing over the use of the word "solution", not saying he doesn't like the workaround which is what I originally thought. It depends on how you read it.
Perhaps they're concerned that seeing an 'undo' button would confuse people about how e-mail works, and they'd get a lot of requests to 'undo' messages that had really been sent. Or perhaps there are enough cases where people really want the message to go instantly that even 30 seconds delay would annoy them.
Source: http://www.searchenginejournal.com/gmail-labs-rolls-out-undo...