@ItWillWash thanks for the advice about getting rid of cookies etc and I'll try this when I get more time.
Thanks again. I've been trying your various suggestions but so far nothing is working. Basically, when I click on the attached file on Roundcube webmail, instead of it opening up as normal, it come up with a long list of all the recently accessed files, each of which is then able to be opened, although the attachment is titled only as the one specific file. I can't seem then to delete all the extraneous added on files.
@GrannyAchingsShepherdsHut , yes I've tried accessing the file from somewhere other than stored in Documents and it still has all the other unwanted documents attached to it too.
@AlisonDonut , when I try just to share a file using the inbuilt email on my PC, for some reason, it tries to open an old email programme I used to use but (very long story) that then 'crashed' my entire email network and so I stopped using it and started just using either webmail for work or gmail for personal. So I can't do it that way but thanks for the suggestion.
@HereIGoAgainAndAgainAndAgain thanks also for these suggestions. None seem to work.
I've now seen that every single Word document that anyone has sent to me, doesn't open as normal anymore. Instead, it also comes up with a list of all documents that I've recently accessed on my PC with the other person's attached document at the top of that long list.
PDF documents that have been sent to me as attachments, all open a OK and only show that one document. So it's something going on with Word documents. and all the attachments I ever send, have to be Word documents. Does that further discovery lead anyone here to think, Ahah! Now I know what's going wrong - or doesn't it really make a difference?