[otrs] No notification after creating ticket through web request

Dear all, We have set up OTRS 2.4.7 on Open Suse 11 and everything seems to work fine, except for one thing. When a customer creates a new ticket by sending an email to our OTRS system, the customer gets a confirmation email with the Ticket# and the new ticket is created by the system (we as agents also get an email). When the customer however creates a new ticket by using the customer.pl website, the ticket is created, but the agent and the customer don't receive a notification of the new ticket by email. Does anyone have an idea? Kind regards, Erik