Log Mail with Log4J SMTP Appender doesn't work

Hello, i want Axon Ivy to send an Email when there is an error so i added this code to "log4jconfig.xml":

< appender name="EmailAppender" class="org.apache.log4j.net.SMTPAppender">
        < param name="BufferSize" value="512" / >
        < param name="SMTPHost" value="smtp.gmail.com" / > 
        < param name="SMTPProtocol" value="smtps" / >
        < param name="SMTPPort" value="465" / >
        < param name="SMTPUsername" value=" *** " / >
        < param name="SMTPPassword" value=" *** " / >
        < param name="From" value=" *** " / >
        < param name="To" value=" *** " / >
        < param name="Subject" value="Testing Log4j Mail Notification" / >
        < layout class="org.apache.log4j.PatternLayout">
            < param name="ConversionPattern" value="%-7p %d [%t] %c %x - %m%n" / >
        < /layout >
    < /appender >

  < root > 
    < level value ="WARN" / > 
    < appender-ref ref="FileLog"/ > 
    < appender-ref ref="EmailAppender"/ >
    < appender-ref ref="ConsoleAppender"/ >    
    < /root >

The FileLog works but i dont receive the email. When i change the order to this:

< appender-ref ref="EmailAppender"/ >
< appender-ref ref="FileLog"/ >

then the FileLog and the MailAppender doesn't work.
When i use the same code in an Eclipse Java Project it works and i get the email.

What should i do?

Edit: Do i have to add mail.jar and activation.jar to my build path in Axon Ivy? In Eclipse i added them to lib and it worked but i don't know how to integrate them to Axon Ivy.

Edit2: With Log4j debug=true i get this Error in my logfile:
2019-01-22 16:21:32.230 ERROR [ch.ivyteam.log.LoggerFactory] [main] [] Log4j: Could not configure java.lang.NoClassDefFoundError: javax/mail/internet/AddressException at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671) at java.lang.Class.getConstructor0(Class.java:3075) at java.lang.Class.newInstance(Class.java:412) at org.apache.log4j.xml.DOMConfigurator.parseAppender(DOMConfigurator.java:247) at org.apache.log4j.xml.DOMConfigurator.findAppenderByName(DOMConfigurator.java:176)
...