The AutoSupport message contains the /etc/messages file. If that file becomes too large, the size of the AutoSupport message can cause problems, especially if you are using the SMTP transport protocol. You should keep the size of AutoSupport messages down.
For more information about editing the /etc/syslog.conf file, see the na_syslog.conf(5) man page.
Using the minimal setting is not advised, as it may impact the quality of your technical support.