Some published web stats on email traffic patterns

In December 2004, the breakdown of a selection of global email traffic, as monitored by Postini and MessageLabs (internet-level managed service providers of email services) was that:

- every 10 in 13 messages were spam (Postini, 2004)

- every 1 in 66 messages is infected by a virus (Postini, 2004) 

- every 1 in 2 SMTP connections were associated with a directory harvest attack (DHA) - where illicit users are, on average, hijacking 30% of an email server’s capacity (Postini, 2004) 

- every 1 in 1024 messages contained pornographic images (MessageLabs, 2004)

Successful DHA attacks can dramatically increase the volume of junk email (spam), forcing unprotected corporations and Internet Service Providers (ISP) to incur higher email system costs, decreased email system reliability and face increased breaches in security. (Postini, 2004)