It allows me to set up lists of things to be sent to certain characters. For instance, I want to send all Frostweave Cloth to my tailor and all Relics of Hodir to my hunter who just turned 80. I posted in the WoW forums asking for an addon that does that, and someone suggested BulkMail2, which does it, but it's kind of clunky and has the above-described bug.
The "send" button can no longer be clicked.
It does work sometimes when I have items for only one alt whose name already happens to be in the "To" box (no idea what that is called in english :p) when I open the mail.
I now use it just to remind me of what I should send where since it still makes the list.
It would be great if this was fixed :)