eMail spam is unwanted bulk eMail. Its like junk mail in your postal mailbox, but it is worse due to its possible danger from malicious programming, loss of privacy, Internet congestion, etc.
From mailing lists.
Spammers regularily attempt to get the lists of subscribers to
mailing lists [some mail servers will give those upon request],
knowing that the email addresses are...
The term spam refers to bulk emails that are generated automatically rather than being individually composed, and which generally are used to advertise products that you wouldn't actually want to buy...
spam, bulk email, unsolicited email. Same as the junk mail your mailman leaves in your mailbox. Over time Spam also has added malicious code. in other words TRASH that takes up all your Email space...