"Failed to process message due to a transient exception" error in message tracking logs

Summary

This article describes an issue in which email messages that contain attachments aren't delivered and Microsoft Exchange Server logs a "Failed to process message due to a transient exception" error. The issue occurs when the drive that hosts the system temporary folder doesn't have enough free disk space for the Mailbox Transport Submission service to process large attachments. The article explains the cause of the failure and provides guidance for monitoring and managing disk space to prevent message submission and delivery issues.

Symptoms

You send an email message that has an attachment, but the recipient doesn't receive the email message.

When you search the Microsoft Exchange Server message tracking logs, you find an event entry that displays the following information:

EventId: "SUBMITDEFER"
Source: "STOREDRIVER"
EventData: "{[ItemEntryId, <item entry ID>], [DiagnosticInfo, Error:RetryMailboxServerError,
Diagnostic Information: Stage:CreateMailItem, SmtpResponse:431-4.3.1 STOREDRV; disk is full 
431 4.3.1 STOREDRV.Submit.Exception:StorageTransientException.IOException;
Failed to process message due to a transient exception with message The message content has become corrupted.
IOException: There is not enough space on the disk.], [DeliveryPriority,Normal]}"

Note

To search the message tracking logs on a specific server, run the following command:

Get-MessageTrackingLog -Server <server name> -Start <start of date range> -End <end of date range> -Sender <SMTP address> -EventId "SUBMITDEFER" -Source "STOREDRIVER" | Select -Property Timestamp,EventId,Source,EventData | FL

Similarly, if you search the Exchange Server connectivity logs, you find an entry that displays the following information:

Direction: ">"
Description: "Failed; HResult: 1140850693; DiagnosticInfo: Stage:CreateMailItem,
SmtpResponse:431-4.3.1 STOREDRV; disk is full
431 4.3.1 STOREDRV.Submit.Exception:StorageTransientException.IOException;
Failed to process message due to a transient exception with message The message content has become corrupted.
IOException: There is not enough space on the disk."

Note: This issue only occurs in Exchange Server 2016 and later versions.

Cause

When you send an email message that has an attachment that exceeds 128 KB, the Mailbox Transport Submission service on Exchange Server 2016 and later versions creates a temporary file in the system temporary folder to process the attachment. However, if the drive that contains the system temporary folder has insufficient disk space to create the temporary file, Exchange Server drops the email message. In that scenario, Exchange Server doesn't send a non-delivery report (NDR) to the sender and doesn't retry delivery.

Workaround

Monitor the free disk space on the drive that contains the system temporary folder to make sure that the drive has at least 1 GB of free disk space. The system temporary folder path is specified by the TMP system environment variable.

Because Exchange Server automatically monitors disk space on the drive that contains the Exchange Server mail.que file, consider setting the path value of the TMP system environment variable to a folder on the drive that contains the mail.que file. In the event of low free disk space on a drive that Exchange Server monitors, Exchange Server records back pressure events in the application log.