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

Question

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

1. Log onto security.microsoft.com.
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."

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

Thanks!

Answer 1

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:

Get-HostedContentFilterPolicy

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="company.com"}

Links:

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/anti-spam-policies-configure?view=o365-worldwide

https://learn.microsoft.com/en-us/powershell/module/exchange/set-hostedcontentfilterpolicy?view=exchange-ps