tep_mail

[ireader]

Hi all,
Is anyone able to shed any light on this,
my email used to be ok, but,
I have recently started to encounter this error, please take a quick look
Thanks all,

Fatal error: Call to undefined function: tep_mail() in /files/home/readergroup/catalog/checkout_process.php on line 346


line 346!

 tep_mail($order->customer['firstname'] . ' ' . $order->customer['lastname'], $order->customer['email_address'], EMAIL_TEXT_SUBJECT, $email_order, STORE_OWNER, STORE_OWNER_EMAIL_ADDRESS);

// send emails to other people

It occurs when trying to create an account or when making a purchase
or trying to update details in admin, etc

however if I use the email function in admin the email is sent fine and notice appears "email sent - " so the email does work,

where should tep_mail be defined?
Is this related to the server or the script, have my files been got at?

I have also had problems with email being delivered to yahoo addys OK
but not to addresses on the same domain as my server,
or to a freeserve address for example, but Yahoo is ok,

osmax 1.7
FreeBSD 4.10-STABLE
Apache/1.3.29 (Unix) mod_perl/1.28 PHP/4.3.5
MySQL 4.0.18