I am looking for help in an unusual issue. I already tried everything in order to resolve the issue.
Here's what we are experiencing: We have an Exchange On Prem Org with Exchange 2016 Servers. On these Server all Antispam Agents were installed when the servers themselves were installed. We now have one mailbox which can't receive from some senders. This mailbox is a shared mailbox and nothing special is configured. The Junkmailbox Config is empty, as well as the senderfilterconfig. The blocked senders Email adresses appear no where. Nevertheless, the agent logs look as follows:
ender Filter Agent,OnEndOfHeaders,RejectRecipients,554 5.7.105 SenderFilterAgent; Sender denied as sender's email address is on SenderFilterConfig list,PerRecipientBlockedSender
Any ideas where else too look?
We are not Using Edge Servers and the affected Mailbox is very old, and big as well (165 GB in total)