seperating new content from quoted content in the body

Hello, thanks for writing this class, very helpful. I was wondering how could I seperate previous quoted messages from the body to get just the reply without the quotes from previous messages.

Any guidance on this would be much appriciated, thanks.

There is no standard rule for that.

Most mail programs start quoted lines with the > character.

You may want to try parsing the message text line by line and consider those that start with > to be quoted text.

is that controled by the mail program that sends the message or that receives it?

No, it is just a common practice of mail programs when editing replies to quoted messages.