[swinog] Any contact to sunrise / chello.at / libertyglobal Postmaster

Hi

We have a case of emails reproducible disappearing to one specific sunrise recipient.

The recipient is quite sure, he has not activated any filtering rule in his sunrise webmail. He requests us as the ISP of the sender, to investigate the issue 'from the source'.

We see in our logs:

mx0.sunrise.ch has address 213.46.255.61

is happily accepting the email with 200 OK. No late bounce can be found.

Does anyone know, how to contact chello.at for such issue? I have tried the contacts registered @ RIPE for this range. They are either 'not in charge and don't know who is' or do not respond. Sunrise seems not to know how to open a case with chello for such an issue (as last time we faced such an issue).