So, one of the companies I work with encountered some chaos in their hybrid MS365 / on-prem deployment.
There is a distribution list (we'll call it [email protected]) which is present on both the on prem and MS365 side of management consoles. However, while on-prem Exchange control panel shows distlist1 as accepting mail from both inside and outside the organization, MS365 has decided to ignore that and ONLY accept mail from 'internal' to the company.
As a result, distlist1 used to receive invoices, etc. for one specific team is getting email rejections and not receiving its mail.
This is unable to be changed on the MS365 side of things, and LOOKS like some kind of disconnect or desync between Exchagne on-prem and MS365.
I'm not sure where to begin looking as to what could cause this on MS365 but if anyone has any pointers of where to look next and fix this so on MS365 it actually accepts the on-prem setting of "allow all to send to list" that'd be wonderful.
Best Answer
Toggle the setting on the on premises object. Initiate an Azure AD Connect delta sync. Wait an hour. Toggle the setting back on the on premises object. Initiate an Azure AD Connect delta sync. Wait an hour.