How do I change the URL that is displayed in Email replies, and auto acknowledgements?

The URL was originally helpdesk.domain.com:8080 but I have this routed through and NGINX reverse proxy so is now only helpdesk.domain.com.

I've followed the steps listed in here: https://pitstop.manageengine.com/portal/en/community/topic/requestlink-displays-https-in-email-notifications, but to no avail. There is no difference.

The changes are being applied, as if I change the $requestlink to 'Test' it makes the changes and is visible in test emails. However, if I set the $requestlink to be 'helpdesk.domain.com' it still adds ':8080' on the end.

Thanks