Occasionally, I get an email with text that looks gibberish! I guess I am seeing HTML instead of plain text

Some emails received with gibberish (HTML?) in text body. So infrequent, that it has not bothered my but now I have received 2 emails from SKy that ARE important. The body text starts "Begin 666’ and ends with ‘End’. I can read them perfectly well in my email on iPad / iPhone but once I open up eM Client, they are received as gibberish and forwarded back to my iCloud account does not render them readable at all. I can go back to the originator and ask for a re-send but is there any solution or work-around that you can suggest?

UPDATE FROM ORIGINATOR : Its definitely NOT HTML or XML but I do not know what it is!