BINGO!! It works!!
It was the following line that caused my problems:
$result = func_send_mail($email, 'mail/acr_review_reminder_subj.tpl', 'mail/acr_review_reminder.tpl', $config['Company']['support_department'], true);
I changed the final parameter to false as you described and now the subject line is readable
I got there in the end - thank you Karina.