Exchange Back Pressure and Safety Net
The following article covers a scenario where 2 Exchange 2013 servers were in the same Active Directory site. There is no DAG in place and the Safety Net settings had the default configuration. Issue: A receive connector was set-up on ExchangeSrv#1 to allow relays from 3rd party of line of business applications. ExchangeSrv#1 had plenty of space, not low on resources and was not in a back pressure condition. A 3rd party system was in place and submitting emails using Telnet. The majority of emails being submitted were being rejected with the error "453 4.3.1 Insufficient system resources". ExchangeSrv#2, did not have the same receive connector configured and was not accepting emails from the 3rd party system. It did however have little of no disk space left on the C:\ drive which also hosted the transport queue file. In the event viewer ExchangeSrv#2 was in back pressure. It was discovered that multiple IIS logs files were consuming space on the C:\ drive of Ex...