How do we set "Only senders in the organization" in office 365 from active directory attribute ?

@DM Kosala Randika Paranathala

This attribute is synced by AAD Connect by default, don't change this attribute from AD account directly, I would suggest you modify this attribute from Exchange on-premises(EAC or EMS), then sync this modify to local AD account, then sync to AAD.

• When "msExchRequireAuthToSendTo" == True, the setting on group will be "Only Senders inside my organization"
• When "msExchRequireAuthToSendTo" == False, the setting on group will be "Senders inside and outside of my organization"

We check whether is this attribute synced by steps below:

1. Open Synchronization Service tool, then check as picture below:
   
2. We can know this attribute is synced by "Group Exchange" rule, then we can check this rule in Synchronization Rules Editor:
   
   If this attribute still doesn't sync in your organization, you could confirm with AAD Connect team.

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Use the "msExchRequireAuthToSendTo" attribute. You obviously need to have the Exchange AD schema extensions.

I have a very similar case, however in the cloud my group's attribute is set on false, I change the On-prem group object to false as well, and when I run the AdSync Delta the on-prem get's rewritten to True.... I have no custom rules what so ever and the only rule I have is an inbound one to the internal domain, that says update, which should, as far as I understand, take the cloud attribute and sync it to the on-prem group.