get plain text version of the generated html page

Hi, I am new here and sorry if it is a novice question. But I've tried to search for the ansers in the board and did not find anything. I use CKEditor to let users generate html emails, and I also want the plain text version of the email in case the email address does not support html emails (basically removing html tags and replace with new lines \n when necessary, etc.) Is there a way I can get it from the http request? If the question is already answered somehwere, can you help to give me the link of the answer? Thanks.