Just one in three emails within business inboxes hold real, immediate value, according to research released by Mimecast, the supplier of cloud-based email archiving, security and continuity. Only 25 percent of email is considered essential for work purposes with an additional 14 percent categorised as being of 'critical importance'.

Mimecast surveyed 500 business users in the US, UK and South Africa on email practices and the contents of the average employee inbox.

It found 11 percent of email is personal, non-work related. The remaining content is functional at best, with an estimated 7 percent of emails inside the average inbox considered to be spam or junk

On average, 63 percent of email comprises internal, employee-to-employee communication. By looking at inbox content on a spectrum of value from junk to critically important information, the research assigned an average value to different types of inbox.

Higher quality inboxes are notably smaller than those of lower quality - by an average of 10 percent (2.53 GB, compared to 2.81 GB, respectively). They are also likely to contain a higher proportion of internal mail.

The research found that larger businesses with smaller inbox sizes are more likely to have higher levels of essential or critical emails.