Most of us have been part of, what feels like, a never ending group email thread but the NHS may have created the most frustrating example of this in the history of email. 

A "test" email was sent out to everyone who works at the UK's National Health Service. This was done in error and prompted a series of angry replies from the 1.2 million employees. 

Speaking to Business Insider, an NHS employee said some 120 replies had been received so far, meaning that more than 140 million emails were sent across their network. Understandably, this clogged their email system, forcing different departments to issue warnings to those looking to get into contact with them. 

If contacting us by email please be aware that there may be delays in responding due to an issue currently affecting all NHS mail.

— NHS Pensions (@nhs_pensions) November 14, 2016

This is the perfect example of why you should never start or engage in a large email thread. Ever.