My Department has an ICT Systems Usage Policy that provides a suite of IT policies governing the use of Departmental ICT systems by all users, with every effort being taken to obtain a balance between IT Security and the usability of Department systems. That Policy includes a section on how limited use of personal email is permitted, subject to the conditions set out in the policy document.
I can confirm, for the record, that I do not and have not used a private email account for Government business in the Department.