Insufficient exchange 2013 C disk space cleanup

Deploy many exchange mail service, with a 1 - C disk space is gradually consumed less than two years after the case of the C disk space mostly customer feedback mail system, basically no other programs are installed and the C drive set aside enough space share today a method to clean up C drive space, you can free up most of the space.
Open the mail server operating system, you can see that I set aside enough space to the C drive to

open the following path, the log file takes up a full 30GB

inside this log can be cleared of


these are IIS logs, safe, reserved day logs, history log can be deleted directly right.
Description: Mail sub-cas and mailbox, which cas log on the server.