Well, I was taught to say “en-ve-lope” at school, but when I went to America for a short visit, I was told by the local people there that I was supposed to say “un-ve-lope” instead of “en-ve-lope”. Hmmm, I wonder which one is correct? Or maybe both are right, just different dialect?
The two pronunciations are used equally often, and both are fully acceptable, CG.
You may well find that the supporters of un-ve-lope are keen for you to know that they know the word comes from the French. Either way it is not a question really of what you are supposed to say. You make your choice and stick to it! I confess I’m a supporter of en-ve-lope.
Incidentally I do like your nickname.