As did I. I wonder if it's common to all Liz's lands, or just our two?

In Canada, it's mailman (although technically it's probably letter carrier). However, we usually pronounce t's in words where they are ignored by others (internet, international, interesting, interact - all these still have that first "t" pronounced in Canada, and the innernet, innernational, inneresting, inneract pronunciations are viewed as US'n). So I would pronounce the '"t" if I had to say the word postman.