error : You must enter at least one recipient email address

[chellofr]

Hello,
I have an error message.
My shop: 2.0.12b
Joomla: Joomla! 2.5.7

When a customer places an order by check, the order is going very well, but a message appears in red at the order confirmation:
"You must enter at least one recipient email address."
I do not know what is this error?

(however well the client receives confirmation of order by email, but by me against, no.)