log4j with openoffice addon -problem

[Yahya Elyasse]

I have developped a openoffice.org addon in java and need to add email notification for fatal errors in my app.
I used log4j SMTPAppender .i wrote a simple test code and it works ok.
when i used this same code in my openoffice application i got the below exception .I'm including activation.jar and mail.jar into my app classpath.
when i user these 2 jars for simple code test it works great.but when i used the code inside my openoffice addon -it just gives this error.
I'm using jdk 1.6 and i can't figure out what's the cause of this problem

thanks for helping

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javax.activation.UnsupportedDataTypeException: no object DCH for MIME type multipart/mixed; 
        boundary="----=_Part_0_16567002.1203681433862"
        at javax.activation.ObjectDataContentHandler.writeTo(DataHandler.java:870)
        at javax.activation.DataHandler.writeTo(DataHandler.java:301)
        at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:1209)
        at javax.mail.internet.MimeMessage.writeTo(MimeMessage.java:1614)
        at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:537)
        at javax.mail.Transport.send0(Transport.java:151)
        at javax.mail.Transport.send(Transport.java:80)
        at org.apache.log4j.net.SMTPAppender.sendBuffer(Unknown Source)
        at org.apache.log4j.net.SMTPAppender.append(Unknown Source)
        at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:221)
        at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:57)
        at org.apache.log4j.Category.callAppenders(Category.java:187)