Strange new pop-up in Outlook for desktop

The pop-up bordered red in this screenshot suddenly appeared today when choosing multiple email recipients from address book while holding keyboard ctrl button.

Now having to pick recipients one at a time !

I have not changed any settings but the UI did change a couple of days ago, presumably due to an automatic update.

Any ideas what's going on here greatly appreciated.

Windows 8.1 on this laptop.

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I have now discovered it is not just Outlook.

The function of the control button has changed - I cannot select a number of any files or folders using it.

This is proving terribly inconvenient now - what's gone wrong ?

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Ignore this now folks, I HAVE SOLVED IT and it's my own fault :-

It's coming from a small utility I installed called TEXTIFY which allows copying of pop-up warning boxes that normally cannot be saved.

But I didn't realise that it was going to work anywhere and not just on those type of boxes.

Silly me had set it to work on the CTRL key - now I have changed it to the ALT key and there's no proble - hooray.

Having said that I might just uninstall it and forget about it.