This thread seems to match my idea the best,
so I'll post my suggestion here.
EL needs an ingame mailing system.
Storage npc will have an extra option "mail".
Large amounts of items can be transferred through mail,
from sender storage to receiver storage.
Payement can also be transferred through the mail system.
If there is mail,
a mail icon will blink somewhere on the GUI in a corner
Here's a raw sketch;
Overview: http://imageshack.us/photo/my-images/41/mailoverview.jpg/
Sender: http://imageshack.us/photo/my-images/215/mailsend.jpg/
Receiver: http://imageshack.us/photo/my-images/853/mailreceive.jpg/
Prompt: http://imageshack.us/photo/my-images/855/mailprompt.jpg/
