Check your antivirus settings. Generally antivirus won't allow to send emails using some other program (log4j). Go to properties of antivirus in your system try and check there you must find one option related to email sending just check or uncheck (if it is checked) it will work fine.
Thank you for your reply. But the fact you pointed out is not the issue with my application .Because, my application has email sending functionalities in Reporting Module and they work fine without any error. Therefore that error isn't just because of the Antivirus settings.
I did a deep google search on this and tried to find whether there's any XML configuration tag that I've missed but couldn't find any missing item yet.
My concern is about the 1st line of the error message.which is,
What is "STARTTLS" and how to issue that command from Log4j Configuration?