It means just read the most recent email you have got, don't worry about any previous ones.

ignore

It's too ambiguous; but the meaning is rather obvious, leave the previous mail and just see the followings, probably from some companies' ads or like book's feedbacks right? Haha, disregard the FORMER one that is below normally doesn't make sense man, lol.

I'm guessing they were typing fast and left out a comma: "Please disregard previous mail, (and) refer (to the) below (text):" (can also say "refer to the following (text): ") "The previous mail" would refer to another email which was sent previously. Refer below just means see below, use the information below, see the following instead, etc.