How to fix 'Client error the operation could not be completed.' when whitelisting

Silo Customer Support Team 25 Reputation points

A customer is having trouble whitelisting domains. They are taking the steps below:

  1. Log onto
  2. Go to Policies and Rules
  3. Click on Threat Policies
  4. Click on Anti-Spam Policy
  5. Click on Anti-Spam Inbound Policy
  6. Scroll down to “Edit allowed and blocked senders and domains”
  7. Click on Allow Domains
  8. Add the following domains
  9. Click Done
  10. Click Save
  11. Wait 10-15 Minutes.

Once they do this, they see the error message: "Client Error- The operation could not be completed. Please try again later. Microsoft has been made aware of this issue."Screenshot 2023-09-12 at 10.44.37

How do they resolve this issue or any help would be much appreciated.


Microsoft 365
Microsoft 365
Formerly Office 365, is a line of subscription services offered by Microsoft which adds to and includes the Microsoft Office product line.
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Accepted answer
  1. lIBenIl-5208 75 Reputation points

    Have this same issue for one of our clients tenancies but for using blocked senders instead, temp work around is to use the exchange online PS module.

    Run this first:


    Likelihood is you'll only have one policy with info in called "Default"

    running the below will return the info of the filter policy. Should be able to see your pre existing blocked senders/domains in the output

    Get-HostedContentFilterPolicy -Identity "Default" | Format-List

    to add to the list you can run the following:

    Set-HostedContentFilterPolicy -Identity "Default" -BlockedSenderDomains @{add=""}


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