check on empty mailbox in notify_no.c

[Christoph R]

Hello everyone.
I'm trying to get a SMS notification to work on incomming mails.
I have modified the "notify_no.c" to call a script that will do the
notification. 
My problem is that I only want to send a notifiaction if the mailbox 
the mail is beeing delivered to is empty.
How can I check in notify_no.c if the mailbox ( the const char *mailbox
parameter) is
empty?

Thanks in advance,

Christoph Riedl