The mailman is a mentioned character of Another Oobi Vacation. Judging by his name, he is most likely the person who delivers mail to the citizens of Abu Doobi. He is mentioned in Jack Attack, where Max mentions that Dave ate the mail man. He is only mentioned at this point, but he has been written in a few future episode ideas.
It is unknown what the mailman looks like so far.
The mailman is mentioned in Jack Attack. He may make real appearences in Season 3.