Notifications (not) clickable

Hello, I use Vikunja Version: v0.24.1-1044-539897ca, ubuntu version.
I receive notification by mail every day of individual tasks an the overdue ones. The links look like clickable, but they are not. I have to go manually to the site for changing items, see comments etc.Not very serious, but not efficient either.

I seem to remember that with Vikunja online everything went smoothly.

Maybe it’s caused by a wrong configuration, I cannot test the email configuration/compilation. Is there anything else I might try?