Sending Mail is simple, IF you have money and can get into the castle. Once inside the inner walls of the castle, click on the Post Office. If you are going to pick up your mail, just click on the mail you want, and then clikc on the button that says something like "Pick up mail"

To send mail, you click on the button that says send mail. On the next screen, you type in the DC name of the person you want to send the mail to, and then select what you want to send to that person from you pack using the scroll bar at the top of the screen to adjust the amount of that item. Once you are finished, make sure you have enough money in you pack to send the item. It costs $1000 per item slot. By this i mean, you could send 1 piece of food, and it would cost $1000 or you could send one billion pieces of food and it would still cost you $100. Once you are satisified with your "parcel", just press done. At any time you with to cancel the mail, just press the back button.

Note: Make SURE to double check the spelling of the name of the character you are sending to.  Mail sent to characters that don't exisit, is lost forever and there is no way to get it back.