As one of the first contributors to this particular thread I am now working with three different solutions, thanks to other contributors to the discussion.:
- using the Gmail app which opens mail hypertext links using Google Chrome
- using the Outlook app configured to open mail hypertext links in Google Chrome
and that gets round the problem of hypertext links not working in the default mail app because the links default to Safari.
Like everyone else, our experience with this bug is haphazard. My wife upgraded her Air 2 64gb wifi cellular to 9.2.1 first and it was fine. I upgraded my similar Air 2 a few days later and got the bug almost immediately. Then for no apparent reason my wife's Air 2 caught the bug! Meantime my iPhone 4s running 9.2 was unaffected. I resisted the temptation to upgrade to 9.2.1.
Eventually I went for a complete reset of my Air 2 (erase all content and settings) to take it back to its original factory mode - allegedly! After taking most of the day to rebuild it I still had the bug! So despite what Apple has told others, a complete rebuild is not necessarily the solution. I am not going to try that again.
So now for my third work-around. Thanks to another contributor I turned off Javascript in Safari advanced settings and Safari search links using Google as the search engine started working and they are still working - most of the time! I did the same for my wife's Air 2 with the same result. However, hypertext links in mail continue to be useless and freeze mail. Even after the rebuild my iTunes tells me I need to update 9.2.1 although my Air 2 tells me my software is up to date.
A couple of weeks ago I upgraded my iPhone 4s to an iPhone 6. Once all set up I found the 6 to be running 9.2.1. It is fine and working normally and tells me it has the latest version of 9.2.1 although iTunes thinks it needs to update 9.2.1!
I do not propose to try 9.3 until this bug is resolved. If Apple is watching - I am writing this contribution on an Acer laptop running Windows 10 very nicely thank you.