If you allow log files to accumulate on the server, they can
consume a large portion of disk space and affect performance. You
should remove log files periodically; however, be sure to leave log
files on the server long enough for you to review files if a
problem occurs with your message flow.
On the Start menu, point to
Programs, point to Microsoft Exchange, and then click
System Manager.
In the console tree, double-click Servers, right-click a
server, and then click Properties.
On the General tab, in Log file maintenance,
select the Remove log files check box.
In Remove log files older than (days):, type the number
of days that you want a file to be stored in the
Exchsrvr\servername.log directory before it is removed.