We have a SharePoint list setup to receive emails and attachments which works fine when emailing that address directly. However, we've recently added it to an existing universal Exchange distribution group and the emails aren't being received by the SharePoint server. I've checked all sub-folders inside C:\inetpub\mailroot and nothing gets dropped in there.
I've confirmed we can add external contacts (such as Gmail) to distribution lists and those seem to go out without a problem.
SharePoint Version: 2016 Foundation
Any ideas how to continue troubleshooting this?