Hello Experts. In our env, we have Exchange 2013 CU21 in a hybrid configuration with Office 365. We also leverage Azure AD Connect to sync our AD with Azure AD, so we are fully in a hybrid scenario, when centralized mailflow. My issue is, I create an office 365 group from Exchange online portal, and select 'Let people outside the organization send email to the group', people from outside the organization still cannot send emails to the group, or any office 365 group for that matter. I've noticed in the Office 365 portal, when i select the office 365 group, i see the option: Allow outside senders --- set to OFF, when i try to change it to ON, it gives an error saying it cannot be done, and if the group has been recently created, please try again. although it has been more then a few days since the Office 365 group was created. People from outside the organization receive a bounce back when they try to email the group saying: Your message can't be delivered because delivery to this address is restricted.
Is anyone else facing this issue, please let me know how this can be resolved. the Office 365 group is successfully being written back to our on-prem AD, and our on-prem Email filtering solution, the email makes it through to our organization but gets rejected...i believe by Office 365.