The contract notice states the agreement will be divided into three lots: one for small volume covering 10,000 mailboxes, the second for medium volume of 100,000 mailboxes and the third is for large volume of 100,000+ mailboxes.
The winning bidder must provide secure email and gateway, mobile device management, white pages and directory service, business partner secure email and an email router, according to the notice.
It also says there is also scope for add-ons such as remote storage and an instant messaging service that users will be able to purchase.
The tender notes that suppliers will be expected to provide multi-tenanted hosted services in order to deliver the benefits of shared services, such as spreading the cost and the management of platforms across a number of organisations.
NHSmail is the national email service used by NHS staff in both England and Scotland. It has email, calendar, diary, directory and storage functions in a secure environment.
It currently has half a million users across 150 organisations, but the NHS claims this number grows each month.
The CCS expects 20 providers to be chosen to deliver the terms of the contract, which is set to last for two years with the option to extend for a further two. It suggests bidders will charge for the service on a per-user-per-month basis.