Has the idea of mail packages and checks ever been tossed around? Greatly beneficial for anyone in business, especially Cartels/Syndis, and for people that don't have as much time to play as they'd like, or in doing business with people in other timezones that would prohibit most interaction.
With contracts, depositing money into someone else's account, etc, I don't think this would be terribly hard to do or excessive in function.
To write a check, it'd have a simple syntax like:
check
It'd create an item, a check for said amount to said person, kind of similar to how the contract feature works. Once the recipient has the check, they go to a bank, use check, and the funds are transferred.
In addition to the obvious uses for business, this way of transaction is of course much safer than physically carrying a ton of gold to give to someone, as a check could only be used by the target designated in the syntax arguement.
Mailing a package could have a similar function as notes/apps with a syntax like:
mail
A charge could be made proportionate to the weight (or perhaps the item level?) of the mailed object, as it would be in reality. This would be a good deterent from abusing this by safely mailing absurd amounts of gear, or absurdly high level gear. Sure, you can mail, it's safe, you know they'll receive it - but with a cost relevent to what it is you're sending.
Abusable by this,
Pieman's DK gets WICKED SWEET EQ, then mails it to his other char.
Pieman's almost condead voker cleans out his bank account and mails it to his brand new paladin!
I think the reason these have never been implemented is the potential for abuse multiplaying. "Sure, both of my chars are elves, they're great friends. I'm sure my other char would love all this stuff I just got off xxx's corpse!"
Edit: Great, Pie beat me to it by 2 seconds.
Abusable by this,
Pieman's DK gets WICKED SWEET EQ, then mails it to his other char.
Pieman's almost condead voker cleans out his bank account and mails it to his brand new paladin!
I have too many people that want to stomp my face at 50 and too many hours invested in my main character to start sending shinies to my other projects, especially when you consider how few rares are available these days in the first place.
As for the money thing? People do that already a ton, just without mail. Drop gold or use a second party to assist.
Have imms watch the IPs of mailers and the recipients to make sure they're not cheating.
I think it is a great idea, however with the potential abuse it may never happen. If only there was a way where your creation and playing ip could be recorded and therefore you could not send things to yourself as another character because the code would deny you. Then this code would automatically flag the attempted CHEATER and a swift ban would be soon to follow. IDEA is very interesting however I wouldn't know how to make it Cheater proof. 
It's already hard enough to check for cheaters and watch IP addresses. With twenty players on, they have twenty IPs to look at, then all the notes they get on a daily basis, then all the prays/tells they're getting.... and the fact that low levels imms aren't supposed to be wizinvis, that just makes it all a pain in the *** for them.
The logic that "since people already cheat, another avenue for it isn't a bad thing. Just make some one else watch it." is broken at best.
I personally hate this idea. But, well, if you like it, you like it.
And why does everyone cry about the freaking rares? I have no trouble getting rares. I get to the point where I find them, get them, and then GIVE THEM AWAY. It isn't hard, they're all over the place. I see more rares now than I did back in 2.0. Also, I'm finding rares in every zone I go to. Dragon Teeth Mountains, High Tower, Labyrinth, Elven Valley, the Ford, Mahn-Tor, Drkysh're woods (or wherever them thar oozes are.), Emiscar Egal, The Bathhouse, Waterfall, Tainted Valley, and that's just the places I saw them last night.
a-g
Have to agree with you on the rares thing, A-G... my recent pinn has had very little trouble picking up a pretty decent set in just two days at 50.
If I also may point out, to transfer funds to someone else's bank account, the recipient must be in the lands.
Too abusable, sadly. Seems like every time there's been a bug or a loop hole, it gets abused over and over and over until it's corrected in some fashion.
IP checks for packages and checks would be pointless. I could abuse this (not that I would...because I'd just get owned and looted anyway) without even leaving my room. Just flip open the laptop, make my check or package, turn on desktop, log other character and gather my loot.
I also noticed a distinct NON-lack of rares lately, I mean, I actually have choices between pieces of eq now...