Exchange - Free space on local disk.

Question

Hi, How much free disk space should there be for mail to arrive correctly? I noticed that if 20gb remains on the local C drive, then mail arrives with great delays.

Answer 1

What you are seeing is probably Back Pressure:
https://learn.microsoft.com/en-us/exchange/mail-flow/back-pressure?view=exchserver-2019

Look in the event logs when this is happening:
https://learn.microsoft.com/en-us/exchange/mail-flow/back-pressure?view=exchserver-2019#back-pressure-logging-information

20GB is way too low however regardless. You should have at least 100GB free in my opinion. I would recommend adding/moving to a new drive and moving the transport queue

https://learn.microsoft.com/en-us/exchange/mail-flow/queues/relocate-queue-database?view=exchserver-2019

Answer 2

Hi @Андрей Михалевский ,

As Andy said, you could check the Event logs to see if there are any related logs with Back Pressure.

In addition, I think you should check the folder size of your Exchange server to see if the Exchange log size or some other files are too large. If so, you could delete some of them.
Or you could enable circular logging to delete the database logs. Configure circular logging for a mailbox database

Then, as for the message delay issue, please try restarting the MS Exchange Transport service and check if the messages were stuck in Queue.
And you can use the Delivery Reports or message header to analyze the process.

Best regards,
Lou

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