Exchange 2010 sp3/Office 2010 Hybrid all inbound and outbound mail is routed through on prem mail gate way server. <o:p></o:p>

Currently, we are running in a hybrid deployment with mailboxes in the cloud and distribution list on prem. We are using an Edge transport server with an edge subscription to connect Exchange 2010 to Office 365 Exchange online. We are required to keep DL on prem due to mail enabled security groups.<o:p></o:p>

When sending from office 365 to an on prem DL "distribution list" that requires authentication the users are expanded in the list and the email is delivered. However, the DL is only expanded if the DL has an approved proxy address "ie @community.com" that is recognized and populated as a proxy address in O365.<o:p></o:p>

My issue is the DL is not expanded when using a "ie @corp.local " proxy address. I understand this is due to office 365 not recognizing corp.local as an approved domain. Although, I thought the edge transport server/edge subscription would create the mutual trusted needed to allow this message to be delivered. <o:p></o:p>

Am I correct in assuming the edge subscription should still process mail sent to DLs using corp.local? My edge server send connector is configured to send to corp.local mail to my hybrid server on prem. Also, I dont have an issue sending to corp.local DLs if authenticated users are not checked. We would like to have some DL still remain authenticated users only. <o:p></o:p>

Hi,

I recommend you post this in Office 365 Forum also, as they should have more professional knowledge and you may get effective solution timely.

Thanks.