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Mail.que Database growing large size and consuming disk space (Exchange 2013/2016)

Disk space is filling up when you checked, found that mail.que Database is consuming.

What is this mail.que?

The mail.que file temporarily stores all emails before it is delivered to the target. It is an ESE database which means it is similar in architecture like an Exchange mailbox database, the edb file.

Below are causes where mail.que grows:


Mail.que increasing might be due to number of reasons, few are mentioned below:


1) Third party antivirus/antispam acting on the queue db and causing it to grow. You can probably disable the 3rd party transport agents and find if it causes the issue. Type get-transportagent and see how many third party agents are running and then run disable-transport agent -identity “agent name” to disable the agents”

2) Monitor your queue for any bundles of spam mails. Because the queue  db growing in size might be because of unwanted  spam emails as well flooding into the queue.

3) Check if there are any large  attachments stuck in outbox which will cause the db’s transport and mdb’s to grow in a larger size.

So here we have two ways while you proceed with troubleshoot…..

1: Recreate the mail.que

2: Move the mail.que to different volume (Drive)

1: Recreating the mail.que Database:

a: Stop the Exchange Transport Service.


b: Rename the Queue Folder or move the folder to another location which will be located in the following path:

C:\Program Files\Microsoft\Exchange


c: Start the Service “MSExchange Transport”

This will create New Queue folder with small size, monitor this for 2 days and check if the size grows.

2: Moving mail.que to different volume (Drive):

 Moving mail.que can be done both by GUI (Exchange Admin Center) as well as from command prompt.

 While moving we need to be careful with the permissions that our profile assigned.

Moving from EAC below are the permissions required:

Network Service: Full Control

System: Full Control

Administrators: Full Control

Note: Both Source Folder (Queue) and the Target Folder (Queue) has the above permissions.

In case of permissions issue allocated to your profile we can follow the below procedure

a: Stop the Exchange Transport Service.

b: Go to file EdgeTransport.exe.config which is located in the following path

C:\Program Files\Microsoft\Exchange Server\V15\Bin

c: Open command Prompt “Run as Administrator”.

Locate to “C:\Program Files\Microsoft\Exchange Server\V15\Bin”


d: Open the EdgeTransport.exe.config using Notepad from command prompt as shown below:


This will Open the Edgetransport.exe.config in notepad

The below screenshot will show you current path


Change the QueueDatabasePath & QueueDatabaseLoggingPath with the new location where you want to move this Queue folder to, in our scenario we have changed this to D:\Queue


And Save this file.

Move all the files which are there in the Queue Folder to New location, post completion start the Service “MSExchange Transport”.


Happy Learning…..


Praveen Kumar

MCTS, MCITP | Exchange Server

Publisher @ Techrid.com