Forum digest from multiple sites

I have managed to configure notifier to send emails about activity in watched threads, but in those emails, links to threads lead to the base lms address instead of a particular site.

For example - I have subsite.example-lms.com in Sites, and some users interact with course forum there. Then, when notifier-scheduler-supervisor pings, emails are generated with new comments in threads. In those emails, links to threads lead to example-lms.com instead of subsite.example-lms.com.
There is only one LMS_URL_BASE configuration parameter.

What can I do to make those links site-aware?