Sad but true, the "lootbag era" came to an ending with the addition of new creature products, making Mailbox less important than they were before. And indeed, High Levels going to the stratosphere of experience made the game less dependent on mailing system for new areas.
But pay attention: Having Royal Mailboxes enabled on a maker character is always good. Also, having the Postman Quest done is essential if you are planning to stay a Free Account for a while.