Called NHS Mail, the scheme has been trialed at ten NHS trusts and will be available across the service in Easter.
The NIA has hired Orchid PR to promote the scheme in a bid to encourage trusts to sign up. Due to the huge numbers of NHS staff - around 1.2m - promotional work aims to include national press coverage and specialist medical publications.
Orchid MD Ruth Stone said: 'If this system is taken up nationwide it is potentially the largest corporate email system in the world... available to everyone from orderlies to consultants.'
Meanwhile, the NHS University, the body's training scheme, will beef up its PR team. Director of comms and information Catherine Hastings said she planned to grow her team from 12 to 18 before the end of the year.