We are using AWS directory service in our company to manage user identities (we want to have all our core infra in the cloud with site to site VPNs between offices and AWS).
We are also using office 365 with their hosted Exchange as a part of our o365 plan. Users, groups etc are being synchronized from our Amazon AD into Azure AD for o365.
Now, when i create a distribution group inside our own AD, there is no possibility to specify whether i want to allow external senders to send mail to it. I don't have Exchange installed and I can't modify my AD's schema, because it is a hosted service and I don't have the "Enterprise Admins" or "Schema Admins" permission. So I can't even run Exchange setup.exe with the option to modify AD schema only.
Office365 doesn't allow me to change that setting with their web admin, because the group is synchronized from the remote domain and i shouldn't be modifying it locally.
However, AWS supports extending your AD schema with their own web GUI, but they require an LDIF file to do that. I would like to use this to add the msExchRequireAuthToSendTo manually, so that it would get synchronized to the Azure AD.
The only problem is I can't find such ldif anywhere, neither can i find all the required meta-attributes (such as OID) of that attribute for everything to work properly.
What is the easiest way to get that attribute into my AWS Active Directory?