[Exim] EXIM and Amavis

Hi!,

I am using exim with amavis for antivirus for, and I am having some
strange problems, when an error message is generated
(unexistent user) or any message that comes with a null in the From:
amavis doesn't send it, I think it just drops the message.
I've read the exim's faq, and all the error messages should be
sent from null.
Has anyone suffered this??

Thanks!!