Email keeps the majority of corporate information formats and channels together, acting as a file server and used from multiple locations. While we've invested time in sorting, filtering, filing and responding, there is a concern around how information is exchanged both between the organization and others, and also within the organization itself.
From a technology perspective, we are mostly concerned with the size of an email inbox and preserving the integrity of the information it holds. These two factors are most likely to slow down the business and impact productivity, the latter also affecting information risk in its various forms.
While the implications of security breaches are significant, the actual risk is manageable for most businesses. This Mimecast research paper looks at the burgeoning number of businesses opting for email to be delivered as a service, resulting in performance and availability issues becoming less acute.