Why has the 'undo change attributes' in the mail email signature box stopped working with the iOS 10.0.2 software update?

I have recently updated to the iOS 10.0.2 on my iphone and needed to replace the (HTML) email signature.

Previously I would open the html email in a web browser, copy it, past it into an email and then send it to myself. I would then open the email I sent to myself, copy it again, go into my mail signatures and paste it into the signature box.

Once this was done it would lose it's HTML formating but I could then 'shake' the device, be given the option to 'undo change attributes', select 'undo' and all would be back to normal as I created the HTML signature.

Now with the new update when I 'shake' the device I get a different message 'undo Set writting direction' if I choose 'undo' as I did previously with 'undo change direction' nothing happens and the HTML signature is still all mixed up.

I would really love a work around for this if anyone can help me as I was half way through setting up a HTML signature's on mobile devices for a company I am doing work for and now I am at a stand still.

I only have a basic knowledge of HTML so it would be great if you technical answers could be dumbed down a bit.

I will be thankful for any assistance anyone can give me!