I used the search function but I didn't find anything similar to it.
This works in Stormwind(and Booty Bay of course). Since 3.2 the auctioneer and the mailbox are really close together,
but there is a thick wall between them preventing most people to access them from one spot.

The blue circle marks the spot from where you can access them both.
Now there are basically 2 ways to do this.
1. Activate the nameplates above friendly units (see Keybindings)

You can then just rightclick the nameplate. This is pretty easy, but if you want to be able to put a little more automation in the whole AH process
it's not a good one, because depending on the number of people around, nameplates are jumping around and don't remain on the same spot.
2. Use macro and the "Interact With Target" Keybinding

Open your keybindings-window and scroll down to the "Targeting Functions" category. There you will find "Interact With Target". Set it to a key you
like. I will give you an example what macros you could use.
Macro for targeting the Auctioneer Jaxon(must exist and be alive, else no target):
Code:
/cleartarget
/targetexact Auctioneer Jaxon
/cleartarget [dead] [noexists]
Macro for closing the AH window:
Code:
/run CloseAuctionHouse();
Get all money from mails(mailbox must be open):
Code:
/script CheckInbox() for m = GetInboxNumItems(), 1, -1 do TakeInboxMoney( m ) end
This is from wowwiki
Get all items from mails(mailbox must be open):
Code:
/script CheckInbox() for m = GetInboxNumItems(), 1, -1 do TakeInboxItem( m ) end
This is from wowwiki
Since the mailbox is not targetable you need to click it. To maximize the chance your autoclicker will hit it I would recommend facing
the mailbox and setting the camera directly above your character.
Quickauctions2
Now if you use Quickauctions2 you can also use the following macros without having to change to the auctions-tab. I guess there will
be also a command for Appraiser, but I don't use Auctioneer anymore.
This is like clicking the "Cancel"-button:
Code:
/run QuickAuctions.Manage:CancelScan();
This is like clicking the "Post"-button:
Code:
/run QuickAuctions.Manage:PostScan();
With these few macros, quickauctions and some kind of autoclicker/autoit you can play the auction house very aggressively without even being present.