I have done as you said and the registry now looks like you say in the filestore. It did previously only have SSL 2.0 as you said.
I have to say I find it quite frightening to be instructed to change registry keys for fear this leads to other problems which I don't understand and cannot fix.
I wasn't really sure how to get into the registry to edit it although I guessed correctly. For the benefit of another poster on here, what I did was tap Windows key, type regedit in search box and double click on the resultant regedit.exe file
I had a bit of trouble initially finding the correct area to edit and found this article helpful https://www.lifewire.com/hkey-local-machine-2625902
I left the server settings in WLM 2012 as they were. When I finished the registry edit I closed WLM and reopened.
At the moment all seems to be working on WLM 2012 (This includes all my other email accounts, which had of course been performing normally anyway. I had had concerns that they might be affected by this registry edit, especially AOL which uses a different protocol). I sincerely hope this will continue. We'll see what tomorrow brings.
Hopefully we will hear from poster para999 whether this helps them too. That person only has one email account which is MSN and he/she uses IMAP.
Thank you for your ongoing help. It is much appreciated.