The NHS suffered a massive email storm today

Don’t reply whatever you do…

Graham Cluley
Graham Cluley
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The NHS email storm | Graham Cluley

As The Telegraph and many other British newspapers are reporting, the National Health Service (NHS) has had its email communications turned to porridge today.

Not by malicious hackers sponsored by a foreign state, but instead by a simple human error that saw a test email sent to some 1.2 million NHS employees.

And, as I explain in the video above, whenever a recipient replied to the message (for instance, “Did you mean to send me this email?”) their response was sent to the other 1,199,999 people on the list.

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Oh dear oh dear.

What happens next? Well, typically other people get angry at the “stupidity” of the people who replied to the email, so they also reply to the mailing list asking that no-one else reply to the mailing list…

You’ve got yourself an email storm.

Which wouldn’t be a life-and-death situation if umm.. it wasn’t the National Health Service which was suffering from email paralysis.

Hopefully things are returning to order by now.


Graham Cluley is an award-winning keynote speaker who has given presentations around the world about cybersecurity, hackers, and online privacy. A veteran of the computer security industry since the early 1990s, he wrote the first ever version of Dr Solomon's Anti-Virus Toolkit for Windows, makes regular media appearances, and is the co-host of the popular "Smashing Security" podcast. Follow him on Twitter, Mastodon, Threads, Bluesky, or drop him an email.

5 comments on “The NHS suffered a massive email storm today”

  1. Ash

    The best way I've found to deal with an email storm is to set up a new filter to send all replies to a new folder. That way it doesn't clog your inbox, and you can get on with your work.

  2. drsolly

    My local GP has no way for me to get in touch with them by email, or by filling in a comment form. The only way I can contact them is to telephone or visit (which needs an appointment).

    I've told them that this is really silly, because dealing with an email is faster than dealing with a phone call.

    My dentist has only just started using computers. And only just started to accept credit cards.

    But the big question I have is, how on earth is it even possible to make a distribution list of a million email addresses!

  3. John Lewis

    Rosalyn (or whoever sent the original email) should not be blamed. The fault lies with the design of the email solution and that lies with the NHSDigital team and their service supplier (Accenture?). If all 1.2m each spent only 15minutes dealing with this it equates to 300k hours. At an average of £50 p.h. that is £15m compensation due.

  4. Etaoin Shrdlu

    The email itself was quite short, with a subject of "test" and no text in the body, but of course when it is copied to a mailing list, all of the recipients get a copy of the list (unless they had the sense to use BCC:, which no one ever does). That means the size of each email was the equivalent of four or five million words. Even a Le Carre novel would only be a fraction of that.

  5. NotaMan

    Ha ha…this happened at work on Friday…I was amazed at how many people replied to all not to reply to all….I just right clicked on an email from the string and chose ignore….

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