log4j configuration example

log4j.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE log4j:configuration SYSTEM "http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/xml/doc-files/log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"
	debug="true">

	<appender name="console" class="org.apache.log4j.ConsoleAppender">
		<param name="Target" value="System.out" />
		<param name="Threshold" value="INFO" />
		<layout class="org.apache.log4j.EnhancedPatternLayout">
			<param name="ConversionPattern"
				value="t:%-6r [%.20t] %-5p %d{MMM-dd-yyyy HH:mm:ss,SSS} [%x]  %c{1} - %m%n" />
		</layout>
	</appender>

	<appender name="rollingFile_old" class="org.apache.log4j.rolling.RollingFileAppender">
		<!-- <param name="Threshold" value="DEBUG" /> -->
		<rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
			<param name="FileNamePattern" value="${LOG_FULLPATH}.%d{yyyy-MM-dd}.gz" />
			<param name="ActiveFileName" value="${LOG_FULLPATH}" />
		</rollingPolicy>
		<layout class="org.apache.log4j.EnhancedPatternLayout">
			<param name="ConversionPattern"
				value="t:%-6r [%.20t] %-5p %d{MMM-dd-yyyy HH:mm:ss,SSS} [%x]  %c{1} - %m%n" />
		</layout>
	</appender>

	<appender name="rollingFile" class="org.apache.log4j.rolling.RollingFileAppender">
		<!-- <param name="Threshold" value="DEBUG" /> -->
		<rollingPolicy class="org.apache.log4j.rolling.FixedWindowRollingPolicy">
			<param name="FileNamePattern" value="${LOG_FULLPATH}.%i" />
			<param name="ActiveFileName" value="${LOG_FULLPATH}" />
			<param name="MaxIndex" value="10" />
		</rollingPolicy>
		<triggeringPolicy class="org.apache.log4j.rolling.SizeBasedTriggeringPolicy">
			<param name="MaxFileSize" value="50000000" />
		</triggeringPolicy>
		<layout class="org.apache.log4j.EnhancedPatternLayout">
			<param name="ConversionPattern"
				value="t:%-6r [%.20t] %-5p %d{MMM-dd-yyyy HH:mm:ss,SSS/zzz} [%x]  %c{1} - %m%n" />
		</layout>
	</appender>

	<appender name="email" class="org.apache.log4j.net.SMTPAppender">
		<param name="BufferSize" value="512" />
		<param name="SMTPHost" value="host" />
		<param name="From" value="from.com" />
		<param name="To" value="to.com" />
		<param name="Subject" value="message" />
		<layout class="org.apache.log4j.EnhancedPatternLayout">
			<param name="ConversionPattern"
				value="t:%-6r [%.20t] %-5p %d{MMM-dd-yyyy HH:mm:ss,SSS} [%x]  %c{1} - %m%n" />
		</layout>
		<filter class="org.apache.log4j.varia.LevelRangeFilter">
			<param name="LevelMin" value="error" />
			<param name="LevelMax" value="fatal" />
		</filter>
	</appender>

	<logger name="package">
		<level value="debug" />
	</logger>

	<root>
		<priority value="info" />
		<appender-ref ref="rollingFile" />
	</root>

</log4j:configuration>

Recommend %throwable{N} to avoid a full stactrace in the mail.
value="t:%-6r [%.20t] %-5p %d{MMM-dd-yyyy HH:mm:ss,SSS} [%x] %c{1} - %m%n%throwable{1}" />