Some Senders are Blocked in Exchange ORG

Marco Freund 1 Reputation point
2021-10-21T13:25:01.713+00:00

Hi everyone,

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)

Thanks

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Andy David - MVP 141.6K Reputation points MVP
    2021-10-21T13:53:05.3+00:00

    I am not a fan of installing anti-spam agents on Mailbox Servers.
    I would consider disabling it.
    https://learn.microsoft.com/en-us/exchange/antispam-and-antimalware/antispam-protection/antispam-on-mailbox-servers?view=exchserver-2019

    Not having said that, is junk mail enabled for this shared mailbox? Maybe disable it and test. 

    Set-MailboxJunkEmailConfiguration "shared MBX -Enabled $false

    Also make sure this is not enabled: 

    Get-RecipientFilterConfig
  2. Kael Yao-MSFT 37,496 Reputation points Microsoft Vendor
    2021-10-22T08:04:08.403+00:00

    Hi @Marco Freund

    If the senders send to other mailboxes in your organization, will the messages also be blocked?
    If the messages will also be blocked, the issue should be caused by the anti-spam agents and not have too much to do with the shared mailbox.

    I am afraid you may need to disable the sender filtering to let the messages pass.
    While as you mentioned, it would also affect other mailboxes.

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