[exim] get email status (C,C++)

Hi.

I use exim4 in Debian Lenny and jwsmtp library as a SMTP client. When
I try to send a email with non-existent "from" email address, exim
answers 250 OK <HASH>, but don't actually send this email (I believe
that "from" email address is bad). How can I determine
programmatically (C or C++) that exim4 didn't actually send this
email? With SMTP calls to exim, exim configuration or something?
Thanks!

--