We are running Exchange 2010 SP3 Enterprise on Windows 2008 R2 Enterprise. 4 Servers: 2 servers with CAS/Hub Transport role, and 2 servers with Mailbox Role. Mailbox Servers are set up with DAG.
All 4 servers are at the same site/subnet. No load balancing configured.
Something I'm trying to understand is with outbound email: 95% of the time emails get routed out through one CAS/HubTransport server and other times, maybe 5%, route out through the other CAS/Hub Transport server. I'm not sure what logic (or configuration) determines why emails get routed out one CAS/Hub Transport server vs the other. Is this something native within Exchange that knowingly changes the outbound path for any particular reason?