Could not execute mail delivery program

[N2O4U]

YaBB SE Version: 1.5.4
PHP Version: 4.2.3
MySQL Version: 3.23.x
Server Platform: Unix, Linux, or BSD
Link to Forum: www.caccautosport.org/yabbse

Problem Description:
When users register and its supposed to tell them that an email is sent with their new temporary password, this error comes up:

I just attempted to register in the new CACC Forum, It accepted my password

and email but the generation and emailing of the password failed and provided

this message;

"2:Could not execute mail delivery program
(/home/caccauto/HTML/yabbse/Sources/Subs.php ln 443)"

and no email is generated.

===

For now i've disabled the mail delivery so anyone can just make an account without an email being sent...  any ideas what's wrong???  Please help thanks...

[[Unknown]]

Probably talk to your host.

Do you have any mods installed?

-[Unknown]