There is no logical reason nor benefit for Herbert to limit his correspondence. He has no one in his life. Communicating with an ex-wife who lives so far away is ‘safe’….
this, as other ridiculous actions Herbert has performed over the years, is part of his self=imprisonment.
That there is no benefit gained is not unusual. That his ‘rules’ have destroyed his life, have left him alone, unwanted, unloved, unneeded, is not grasped.
This is an example of how people imprison themselves.