From the shop
You can buy Harbor mail at Slateport City
To get the harbor mail you need to go to slateport city
slateport city Pokemon mart
Slateport city Mart
you go to the slateport city mart and you can buy it
You can find an harbor mail in Slateport City Hope I Helped By Matthew Teves
You go to Slateport city and go to Pokemon market. Here you can buy Harbor mail.
the place where you give that guy the Devon goods (a.k.a slateport city)
yes. you go to slateport city and there should be some at the mart
Go to slateport city and go into the pokemart and talk to the cashier he will be selling harbor mail.
Slateport City doesn't have a gym.
I believe you can find it in Slateport City in the market area. One of the people in the market area will sell Harbour Mail.