The extension point PostSendMessageListener is a java interface you can implement to perform actions after the message has been sent successfully.
Your plugin receives the sent message as a
javax.mail.Message and other parameters containing additional information about that message. Any changes to the the sent message will be without effect.
Please note that the parameter
answerType specifies the type of the operation. In most cases the
AnswerType.DEFAULT indicates the sending of the final answer of a ticket. But there are also other types of answer operations e.g. intermediate reply or confirmation messages. When implementing this extension point you have to decide which types of answers you need to process to fit your requirements.