A global plague of spam, combined with tighter email retention policies dictated by government and industry, is severely increasing storage costs.

According to analyst IDC, the dramatically increasing cost of storing and managing email throughout its life-cycle is driving the need for better management of email-based collaboration and content.

Some 12 billion spam messages will be sent daily next year in North America alone, in addition to 13 billion person-to-person emails and six billion email alerts and notifications, the firm predicted.

Last year the size of business email volumes sent annually worldwide exceeded one exabyte (one billion gigabytes) for the first time.

"Email is frequently the point of entry for spam, viruses, and other IT headaches, and users often struggle to keep up with mail overload, regulatory compliance and inbox management," said Robert Mahowald, research manager for IDC's collaborative computing service, in a statement.

"Add to that the fact that more email-capable mobile devices mean increased mail volume and mailbox synchronisation and management.

"These new threats - and opportunities - for the future of the inbox mean that email proponents will need to find ways to improve its security and flexibility without sacrificing its usefulness."