Who caused the last major ‘reply allpocalypse’?

Have you ever been caught in an email chain where someone hits "reply all" instead of just "reply"? Have you ever been caught in an email chain of more than 1.2 million colleagues? Unless you work for the UK's National Health Service (NHS), chances are you have not.

On Monday, an IT contractor sent out a “test email” to all NHS employees — which was only exacerbated by people hitting "reply all" asking to be taken off the list. Per various reports, the incredible strain on the NHS email servers resulted in slow NHS email performance and email delivery delays from both internal and external sources.

People took to Twitter to comment on the situation.