Email storm

An email storm (also called a reply all storm or sometimes reply allpocalypse) is a sudden spike of "reply all" messages on an email distribution list, usually caused by a controversial or misdirected message. Such storms can start when even one member of the distribution list replies to the entire list at the same time in response to an instigating message. When other members respond, pleading for the cessation of messages, asking to be removed from the list, or adding vitriol to the discussion this triggers a chain reaction of email messages. The sheer load of traffic generated by these storms can render the email servers inoperative, similar to a distributed denial-of-service attack.
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.