An e-mail storm
is a sudden spike of Reply All messages on an email distribution list
, caused by one misdirected message. It starts when multiple members of the distribution list reply to the entire list at the same time in response to the misdirected message, indicating that it was sent in error; this causes other members to reply that the reply is unwanted too; if enough members reply to these unwanted messages, this triggers a chain reaction
of increasingly nasty appeals to be removed off the distribution list or to stop sending messages.
Email storms have the potential to take down email servers due to the sheer volume of traffic they generate.
Some email viruses also have the capacity to create email storms, by sending copies of themselves to an infected user's contacts, including distribution lists, infecting the contacts in turn.
On October 3, 2007, an email storm was generated at the US Department of Homeland Security, causing more than 2.2 million messages to be sent, and exposing the names of hundreds of security professionals.