On RedHat Linux 7.0 you must install the db3-devel RPM before you can compile the Postfix source code.
Warning: do not use multiple Berkeley DB versions. Every Postfix program will dump core when it is built with a different Berkeley DB version than the version that is used by the system library routines. See the DB_README file for further information.
On RedHat Linux 7.1 procmail no longer has permission to write the mail spool directory. Workaround: chmod 1777 /var/spool/mail.
LINUX syslogd uses synchronous writes by default. Because of this, syslogd can actually use more system resources than Postfix. To avoid such badness, disable synchronous mail logfile writes by editing /etc/syslog.conf and by prepending a - to the logfile name:
/etc/syslog.conf: mail.* -/var/log/mail.log
Send a "kill -HUP" to the syslogd to make the change effective.