I recently started migrating users to Exchange Online, while continuing to use Exchange Online. However, since upgrading, I noticed that incoming emails my on-premiseSharePoint libraries/lists (list@sharepoint.domainname.com)are no longer working. Initially, users were receiving NDR's, whichmakes sense. Technically, these emails are coming from outbound, and my Exchange server won't relay to the subdomain we're using.
So, I used these instructions to get past that: http://ezoltan.blogspot.com/2015/11/error-sending-email-to-subdomains-from.html. Basically, it uses my on-premise Exchange server to relay emails addressed to sharepoint.domainname.com.However, my NDR messages were replaced by "Invalid recipient" messages from myanti-spam appliance, which was easy to fix, byadding a subdomain to the anti-spam appliance. But, now those same...