E-mail spam is also known as junk e-mail i.e. it’s a subset of spam that
involves nearly identical messages sent to numerous recipients by e-mail. A common synonym
for spam is Unsolicited Bulk E-mail (UBE) and the definitions of spam usually include the
aspects that email is unsolicited and sent in bulk.
Anonymous: real spam is sent with spoofed or harvested sender addresses to conceal the actual sender.
Mass mailing: real spam is sent in mass quantities. Spammers make money from the small percentage of recipients that actually respond, so for spam to be cost-effective, the initial mails have to be high-volume.
Unsolicited: mailing lists, newsletters and other advertising materials that end users have opted to receive may resemble spam but are actually legitimate mail. In other words, the same piece of mail can be classed as both spam and legitimate mail depending on whether or not the user elected to receive it.
