One specific domain can't receive emails from one specific SES account

Hey,
I have two applications which send transaction emails through ses accounts. Both ses accounts are in production mode and working fine.

The first of this apps is suffering from a problem that emails to the domain henkel.com/henkel.de are beeing send without errors in smpt relay but never reaches the recipient. The recipients are not on account suppression list. The verified identity has feedback notifications configured and when sending to any other domain we get delivery or bounce messages. But when sending to any henkel recipient, we don't get any messages. After some days the email still don't arrive and there are still no bounce messages triggered. The emails just disappear into nirvana.

The second app is able to send to the same henkel recipients and everything is OK. Both apps uses smpt relay with right credentials. Both apps are on eu-central-1.

I will send further informations like account ids to someone via pm.
Thanks
Alex