tempfail for bar LF

Hello!

I am running 8.17.1.9-2+deb12u2 from Debian.
This has been patched to handle bare LF/CR chars.

I now have a broken Cyrus calendar server that sends bare LF:

sendmail[65816]: 48M8gGlI065816: collect: relay=localhost, from=<mm@dorfdsl.de>, info=Bare linefeed (LF) not allowed, where=body, status=tempfail
cyrus/https[65811]: smtpclient: unexpected response to EOT: code=421 text=4.5.0 Bare linefeed (LF) not allowed

Is there a special reason for the tempfail in that situation or should
that be a permanent error? Mail will be sent to the MSP, if that
matters.

--
kind regards
Marco