OK, so I have been tracking this issue for some time now and it is driving me a bit crazy. Here is the scenario:
We have a growing number of Xerox machines in our printer fleet, as we are migrating from Canon printers to Xerox. All of our users use Scan-to-Email when they need to scan something. However, if there are a number of sequential scan-to-email jobs from one printer, somewhere between job number four and job number eight, the SMTP relay in Exchange will go unresponsive to that printer for 3-5 minutes. Once that time has passed, the printer can again send email jobs as normal.
In testing, I have hooked it up to our Xerox vendor's SMTP relay and it does not have this issue. Obviously the problem is in our Exchange deployment, but I'm not sure where to look. We have an on-premise deployment of Exchange 2013, but that will be upgraded soon as we are in the middle of deploying Teams and that will require us to upgrade our Exchange deployment for the calendar integration. Any advice/help is appreciated.