Users mailboxes hosted on my Exchange 2016 started facing issues in receiving the email, and the sender were receiving an NDR with the following error:
I checked all of my Exchange Servers queue size C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\data\Queue\mail.que is around 10GB on all of them.
Generally, it is referring to Back Pressure; in short, Back pressure is a system resource monitoring feature of the Microsoft Exchange Transport service that exists on Mailbox servers and Edge Transport servers.
Back Pressure monitors mainly the following criteria’s in Microsoft Exchange:
- DatabaseUsedSpace[%ExchangeInstallPath%TransportRoles\data\Queue]: Hard drive utilization for the drive that holds the message queue database
- PrivateBytes: The memory that’s used by the EdgeTransport.exe process.
- QueueLength[SubmissionQueue]: The number of messages in the Submission queue.
- SystemMemory: The memory that’s used by all other processes.
- UsedDiskSpace[%ExchangeInstallPath%TransportRoles\data\Queue]: Hard drive utilization for the drive that holds the message queue database transaction logs.
- UsedDiskSpace[%ExchangeInstallPath%TransportRoles\data]: Hard drive utilization for the drive that’s used for content conversion.
- UsedVersionBuckets [%ExchangeInstallPath%TransportRoles\data\Queue\mail.que]: The number of uncommitted message queue database transactions that exist in memory.
More details regarding Back Pressure is available on the below link:
Solution:
Run the following commands on your Exchange Server:
[PS] C:\Windows\system32>Get-TransportServer “servername” | fl
Make sure that “PipelineTracingEnabled = False”
If not then disable it by running the following command:
Set-TransportService Mailbox01 -PipelineTracingEnabled $false
Then Run,
[PS] C:\Windows\system32>Get-TransportConfig
Make sure that MaxDumpsterSizePerDatabase = 18 MB (18,874,368 bytes)
It should always be in MBs only.
Then check Queue:
[PS] C:\Windows\system32>Get-Queue
MessageCount = 0
Then stop Microsoft Exchange Transport Service:
Move “mail.que” to another location or Delete it.
Then Start the transport service again and check the mail flow.
For clearing Exchange Server logs, refer the below link:
https://ammar.cloud/clear-out-logs-for-exchange-2013-2016-2019/
