403 forbidden when DMing

I tried to DM a Lemmy user. This URL was associated to the mail icon:

https://fedia.io/u/@Servais@discuss.tchncs.de/message

That gives a 403 forbidden. I use Tor but neither fedia nor discuss.tchncs.de are tor-hostile. So I doubt Tor is related.

I have to say apart from the above issue, fedia has been working smoothly lately. I’m glad the internal server errors that plagued the system have apparently been resolved AFAICT.