Reb Eliezer, your comment about אל תרבה שיחה עם אשה, seems to indicate you’d have no problem with a man having a female Pen Pal (or email pal) that they write letters to each other every few days, for long periods of times, since it fits into the criteria you established that they haven’t met each other and they don’t see each other or hear each other.
Is this your own boich svara or do you have any source for this criteria you established?