When i want to send the message to the firstname.lastname@example.org its saying the account is not synchroniser with imessage.
Likely it is an email address, not an iMessage address.
Go back to the page from which you asked this question (http://support.apple.com/kb/HT5821). It says "To report unwanted iMessage messages to Apple, please send an email with the following details to: email@example.com [...]" (emphasis added).
Retrieving data ...