Starting January 2026, this is not possible any more. Any forwarded mail is lost, resulting only in an error message in the user's ULCN mailbox.
You have to remove forwarding for ULCN mail yourself if you set this up previously. Follow these steps to remove a previously set forwarding rule:
s plus your student number)Email and then RulesNote: if you never set up a forwarding rule, you don't have to take any action to remove it. However, do check your ULCN mailbox regularly, since there are occasionally mails from the university that are sent to ULCN only and not to your preferred address.
A ISSC helpdesk information page is (used to be?) available in the ISSC helpdesk.
Anyway, we have made available these instruction directly in this PDF.