The List of Officers of the Department of Posts & Telegraphs, Corrected up to 1 July 1935, p. 2 (ref: V/13/261), gives the following range of categories for European or European-lifestyle employees:
E = European (non-Asiatic domicile) [meaning: Europeans born and bred; don’t live permanently in India]
D.E. = European (Domiciled) [meaning: Of uncontested European ancestry; settled in India]
A = Anglo-Indian [meaning: Mixed-race ancestry; living European lifestyle; settled in India]
A.-N.A.D. = Anglo-Indian (non-Asiatic domicile) [meaning: Mixed-race ancestry; living European lifestyle; settled somewhere other than India, e.g., Singapore, East Africa, Hong Kong]
Plus there is an I.C. category for Indian Christians.