Inbound e-mail is building up in the delivery queue with 452 4.3.1 Insufficient system resources as an error message.
Messaging Gateway (SMG) with on prem Microsoft Exchance 2007, 2010 or 2016
452 4.3.1 Insufficient system resources.
The downstream e-mail server is responding to the SMG's attempt to deliver messages with "452 4.3.1 Insufficient system resources". This causes the SMG to retry delivery of the message.
The SMG appliance is working as designed. The issue lies with the downstream e-mail server. Queue errors that indicate an internal problem will have the "[internal]" string added. You may wish to re-route the messages to a working MTA until the issue with the downstream e-mail server is resolved.
Imported Document ID: TECH139775
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