HackTrick

3) Spam :- Every e-mail account and network on the internet has limited space and bandwidth. This means that if an attacker is able to clog up all the inbox space and bandwidth of the target computer, it could cause lot of inconvenience and unnecessary trouble. Spam e-mails have slowly but surely started clogging up the bandwidth on the internet and the memory space in our inboxes.

MailBombing:- Mailbombing is a technique wherein the attacker floods victim's e-mail account with an extremely large (sometimes infinite) number of unsolicited meaningless e-mails. Two different types of mailbombing are-

a) Mass Mailbombing
b) List Linking Mailbombing