I had exchange 2010 installed on a standalone windows 2008 R2 server.
I migrated all mailboxes to a VM running on a windows 2008 R2, using HyperV.
I can send emails super fast. But emails coming in are SUPER slow. sometimes it takes up to 2-3 hours to receive the emails. on random occasions emails are delivered IMMEDIATELY.
I went on exchange connectivity test website and ran the INBOUND test and go tthe error messages attached.
I decommissioned the old exchange successfully, so it's only one exchange server on the network.