An extension to automatically convert an email address to a mailto link makes sense and probably exists
I see no problems on such extensions but I'm not sure if I would call them 'e-mail extractors'. I see an 'e-mail extractor' tool as something that scan a page looking for e-mail addresses and build a list with them to be used later.
Try with:
Ctrl + Shift + E > Developer Mode > Copy Extension ID:xxxxxxxxxxxxxxxxxxxx
Then close Opera and go to Opera profile > Local Extension Settings (folder) Search for the ID extension folder (if exist) and rename it.
Meanwhile, it appears that Opera has virtually no extension available which might replace what it ostensibly did--report on websites' reputations. There are also extensions/services--no on Opera--which do other safety checks. At this point, the only thing that I have been able to get to work is Avira Browser Safety, which does mark search results. Many of the alternatives (to WOT) won't work with Opera, even some Chrome ones (like Bitdefender TrafficLight). Many are free, if they work on your browser. Is Opera coming up with its own solution, and that is why there is nothing in the extensions "store?"
in google chrome, if you install an extension from outside the chrome webstore, google chrome will disable it each time you start the browser. perhaps its the same in opera?