Exchange Admin wants to restrict the send mail access or to limit the access to internal organization sender for sending email to specific distribution lists in O365 Exchange Online.
The task is simple, The admin can navigate to ‘Active teams and groups‘ in M365 Admin center or ‘Groups‘ in Exchange Admin center if the customer exchange service available only on Microsoft 365.
In Many case, Customer uses the Hybrid concept that sync the users and groups from On-Premises Active Directory to Azure Active Directory. When making the changes via the Exchange Admin Centre or Exchange server is not in place to perform the mentioned tasks in EAC, It would advise the Exchange Admin to perform Attribute change in On-Prem AD.
The value “msExchRequireAuthToSendTo” used for limit the send mail access only to Authenticated Senders which means internal user can send email to the specific group and discard the email from outside sender.
AuthOrig – Authorized Originators: accept email from the specified the users.
UnauthOrig – Unauthorized Originators: accept email from anyone but from the specified the users.
dLMemSubmitPerms – Authorized DLs: accept email from the specified distribution lists.
dLMemRejectPerms – Unauthorized Originators: accept email from anyone but from the distribution lists.