How much of a problem is spam? Well, that depends on who you are and how ubiquitous your e-mail addresses are. Absa, a bank that offers its customers free e-mail services, is probably fairly representative of what it's like at the top-end, both as an ISP and as a business.

According to Christo Vrey, who is in charge of digital channels at the bank, its ISP operation receives roughly 18 million messages a month, 14.5 million (or 80 percent) of which are classified as spam. With just over 122 000 subscribers, this works out to slightly less than 120 messages per user per month.

Within the bank itself, he reports that 60 percent of the approximately one million messages received daily are spam. In the context of about 29 000 e-mail-enabled employees, that's over 1 000 messages per user per month.