how do I save photos from my email to photos app on ios 10?

The option is still there. You have to hold down on the image a little longer and then when the save or copy to window opens up, Save Image is on the bottom row but you may have to swipe to the left to reveal it. Once you find it, you can reorder the options by dragging the 3 lines on the right up or down as you see fit.

I noticed that it is not possible to save photos from email if you hold your phone in portrait mode. If you turn your phone in landscape position, then you can save the photos by the suggesred method.

It still works for me in Portrait Mode. It works in either orientation.

Well, it did not work on my wife's iPhone 6s plus. If it works on your iPad, does not prove that it works on all devices.

I Didn't say that it works on all devices. My comment was made to refute your comment that it doesn't work in portrait mode. Here is a screenshot from my iPhone.

Just because it doesn't work on your wife's iPhone does not mean that it doesn't work in portrait mode on iPhones.

MY friend has sent me an email containing 30 photos which I want to save to my photos app. If I use a long press on the first photo it gives me the option to save 30 photos but when I tap this option it only saves the first photo to my photo app. What am I doing wrong?

This doesn't appear to work in Portrait mode on either my iPhone 6S plus and my wife's iPhone 7 Plus. It works in landscape but not in portrait. Very bizarre.