Messaging Server creates a separate set of log files for each of the major protocols or services it supports including SMTP, IMAP, POP, and HTTP. These are located in msg-svr-base/data/log. You should monitor the log files on a routine basis--especially if you are having problems with the server.
Be aware that logging can impact server performance. The more verbose the logging you specify, the more disk space your log files will occupy for a given amount of time. You should define effective but realistic log rotation, expiration, and backup policies for your server. For information about defining logging policies for your server, see Chapter 25, Managing Logging.