You can use command below to cover this group from a Global group to a Universal group:
Get-AdGroup "NewGroup" | Set-ADGroup -GroupScope Universal -GroupCategory Security
You can use command below to enable email for this group(You will could see this security group from Exchange on-premise):
Enable-DistributionGroup newgroup
If the domain name has verified on your Office 365, this group will be sync to Azure AD with AAD Connect.
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