Mule's never really work anyway due to the ridiculous restrictions on it.

You have to log out of main character.
Log into Mule.
Send ~8 Items.
Log into main.
Collect items.
Occasionally:
Log Out of Main.
Log In to Mule.
Send another 8 items.
Log Out of Mule.
Log into Main.
Collect items.
rinse and repeat.

The only way separate characters would work properly is if their is a command to collect from the mule, or you can send more than 8 items.