I have enabled the SMTPAppender for threshold level "ERROR". After that when an error occurs in the application the server.log is showing like:

2012-01-27 14:20:58,565 FINE [javax.activation] (http-127.0.0.1-8090-1) MailcapCommandMap: createDataContentHandler for text/plain
2012-01-27 14:20:58,565 FINE [javax.activation] (http-127.0.0.1-8090-1) search DB #1
2012-01-27 14:20:58,565 FINE [javax.activation] (http-127.0.0.1-8090-1) got content-handler
2012-01-27 14:20:58,565 FINE [javax.activation] (http-127.0.0.1-8090-1) class com.sun.mail.handlers.text_plain

No other mail sending errors are shown. What does this log actually means?

Why the mails are not getting send?