When senders maliciously try to cripple a mail server by sending more messages than the server can handle in a specific time frame, it is called mail bombing or list bombing.
It is possible to have a large number of mails filling up the disk space of the recipients on the server. Other times, the server may be burdened with more than what it can handle, forcing it to shut down. These situations are called mail bombing.
Mail bombs used to be a means of punishing internet users known to have violated netiquettes, for instance, users who use email for spam or unsolicited advertising. Asides from inconveniencing the target, mail bombs affect everyone on the server.
Sending mail bombs may expose the senders to reprisal mail bombs or legal actions.