Issue:
The Exchange server keeps deleting message tracking logs before they are scheduled to be deleted.  They should stay on the server for 30 days, but they often delete at the 10-15 day mark.  The Log directory currently has 1GB of logs.

Solution:
Exchange 2007 and 2010 place retention policies on message tracking logs in three ways: Age, Directory Size and File Size.  In this situation the problem is being caused by the Directory Size limit.

1. First determine what your message directory size settings are currently at by running ” Get-transportserver | select name,*message* ” from the management shell.
2. Look at the number next to MessageTrackingLogMaxDirectorySize.  In 2007, the default is 250MB.  In 2010, the default is 1GB (1024MB).
3. Since the log directly is currently maxed out at 1GB, this directory size limitation needs to be raised to 2GB.
4. From the management shell, run ” Get-transportserver “transportservername” | Set-TransportServer -MessageTrackingLogMaxDirectorySize 2048MB “