sorry I should read the question...
Occupied countries - communicating with the enemy - so that was out.
But what about Vichy France ?
Clearly post to the Empire and America continued at a slow pace.
All telephone calls (since all were hand connected) had to have 'war value'/content. - see Hang out more flags - but I am sure this was relaxed.
Post to Germany for POW camps continued - and were censored.
by both sides
Actually I thought all mail was censored but the sites say only a proportion. Censored material was scratched out not blacked out so there was a hole in the paper. One of my father's letters has..... ' SO many Italians tanks were lost but we all say that ..... Italian tanks are worth one German
and the ..... is a hole in the paper and there is a little slip glued :
" H M censor considers the ratio of worth of Italian to German tanks is classified information. " - but that could be a war time 'joke' by a bored censor.
Censorship is not new, you know - I have a censored post card from Ceylon ( P O W / internment / concentration camp) from 1901.
( Boer POW to my then spinster English grandmother - always wondered what was going on there...)