A postmistress is a woman who is in charge of a post office — the same job as a postmaster. The word is built the old way: master for a man in charge, mistress for a woman in charge. You still meet it in older books, village stories, and some official names, though actually many people now just say postmaster for a woman too, because the job is the job. It is not a rude word here. It is also not the other, private sense of mistress that students often know first. In today’s English it can sound a little old-fashioned, like headmistress beside headteacher. Kind, clear speech can use postmaster for anyone, and keep postmistress when a text from an older time uses it.

女郵政局長（現在也常直接說 postmaster）