原来我只是把属性都弄错了。应该：
#ConFIGURE SMTPlog4j.appender.email=org.apache.log4j.net.SMTPAppenderlog4j.appender.email.SMTPHost=mail.mydomain.comlog4j.appender.email.SMTPUsername=myuser@mydomain.comlog4j.appender.email.SMTPPassword=mypwlog4j.appender.email.From=myuser@mydomain.comlog4j.appender.email.BufferSize=1log4j.appender.email.evaluatorClass=TriggerLogEventlog4j.appender.email.layout=org.apache.log4j.PatternLayoutlog4j.appender.email.layout.ConversionPattern=%m
