SMTP Status: 452 4.3.1 Insufficient system resources

Products

• Messaging Gateway
• Messaging Gateway for Service Providers

Issue/Introduction

Inbound e-mail is building up in the delivery queue with the Last Error of 452 4.3.1 Insufficient system resources

To	From	Date	Route	Size (bytes)	Last Error	Next Attempt	Total Attempts
[email protected]	[email protected]	Wednesday, Aug 9, 2023 04:30:53 PM PST	Default-Local-Route	32345	452 4.3.1 Insufficient system resources	Pending	1

Environment

Messaging Gateway (SMG) with on prem Microsoft Exchange 2007, 2010 or 2016

Cause

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.

This usually indicates that the destination server has run out of disk space or some other resource which is preventing it from accepting email.

Resolution

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.