So if my back end servers, my Hub, CAS, etc. go out, does the Edge Transport Server role buffer my email until the others come back online? Thanks.
It does hold on to the mail. There are internal queues that you can look at if you dig enough. I believe they're in the Extra Tools sections. I don't have the management console in front of me so don't know for certain. The queues are in there right next to the backed up outbound queues.