Mail-Enable an Existing Universal Security Group in Exchange

If an Active Directory universal security group must also receive email, mail-enable the existing group with Exchange tools. Do not create a second distribution group with the same membership unless there is a specific design reason.

Check the group first

Get-Group -Identity "App Support"

Confirm the group is the intended universal security group and review its owners/membership.

Mail-enable it

Enable-DistributionGroup -Identity "App Support" \
  -Alias AppSupport

Verify

Get-DistributionGroup -Identity "App Support" |
  Format-List DisplayName,PrimarySmtpAddress,RecipientTypeDetails

Then configure the primary/proxy addresses and delivery restrictions required by your organisation. In hybrid environments, make the change in the authoritative Exchange/Active Directory system and allow directory synchronisation to complete.

Security: a mail-enabled security group still grants whatever permissions the underlying security group already had. Do not change its membership casually just to alter an email distribution list.