confirmed spam

Hello,

we have a strange issue with the SPAM filter.

Inbound and Outbound Messages to a specific E-Mail-Domain will be recected with the following messages (SMTP-PROXY Log):

Outbound:

id="1003" severity="info" sys="SecureMail" sub="smtp" name="email rejected" srcip="192.168.1.210" from="ME" to="SENDER" subject="SUBJECT" queueid="1SK7cF-00054z-29" size="64324" reason="as" extra="confirmed"

Inbound:

id="1003" severity="info" sys="SecureMail" sub="smtp" name="email rejected" srcip="10.10.10.1" from="SENDER" to="ME" subject="SUBJECT" queueid="1SK6G4-0003zo-27" size="1482975" reason="as" extra="confirmed"

Information: We have anonymized from, to and subject

We checked RLB Listings for this specific E-Mail-Domain -> not listed anywhere.

All we can do now is to write an exception for the involved E-Mail-Addresses. Since we have a smarthost, we can't only write an ecxeption for the Mailserver.

How can we figure out why this E-Mail-Domain is blocked?

Best regards

Martin