Took a free transfer forgetting that the character had unopened mail. The free transfer wasnt blocked because of the mail and the mail disappeared. Neither the sender, nor receiver has the mail items. What happened and why was I able to transfer with unopened mail?
This was also unsuccessful: https://us.battle.net/support/en/help/product/wow/197/1674/solution
Not too sure that anyone is going to be able to answer that for you. The transfer should not have been allowed with the mail pending. Unfortunately, free-transfers I don’t believe can be reversed, and even if it was, I don’t know that the mail would show up 
I’d recommend posting this as a bug in the Bug Report forum.
Thanks. Ill try that.
You could try submitting a ticket here.
https://us.battle.net/support/en/help/contact/464/ticket
Explain what happened and explain that you tried the self-help tool and it failed. No guarantee that they can help, but it won’t hurt you to try.
#dfmb