A few minutes ago I tried sending a comment to
https://todo.sr.ht/~kvo/taskcollect/15 via email. I received an
automated email response with error 550 (Undelivered Mail Returned to
Sender). Specifically, the most relevant error messages seems to be
this one:

	internal system error (in reply to end of DATA command)

And this one:

	Diagnostic-Code: smtp; 550 internal system error

Attempting to submit a comment via the the web interface also fails: I
get "500 Internal Server Error".

Never mind, it must have been a temporary issue. I tried again several
times (through the web interface), and after a few minutes it worked.