I'm floundering around in the dark here, so please take my post with a large portion of salt, and see what others have to say as well.
I assume that these emails that keep reappearing are the same ones? What I mean is, same date and time as the ones you have already deleted?
Try a test. pick one of these, and don't delete it. Does a duplicate appear the next day? If they are not identical, (same time and date), then it's the spammers sending you repeat emails.
Does this email account also have Web Access? Can you access this email account via a web browser? I use Thunderbird for my email management but my email account, provided by my ISP, also has web access. When I visit the web side of my account I can see loads of Spam emails that don't get downloaded to my computer. The ISP marks them as spam and places them in a Spam folder. But if they haven't done that for particular emails and it just sits in the Inbox, they may get downloaded again.
If that's the case with you, make sure proper message rules are set up in the web account to delete those Junk folders regularly, and also the Deleted folder.
Also, look up IMAP. I don't know much about it. Most email accounts are POP but some are IMAP and as I understand it, IMAP accounts duplicate everything in all folders when downloading to email software like Outlook or Thunderbird, etc.
It's all a bit thin I'm afraid, but I hope it helps.
I noticed something in Outlook that I didn;t have in the earlier version I was using. I like to keep my inbox tidy and my junkmail folder emptied. So, I delete my emails as I read them or ove them to a different folder if I want to keep them. And I always do the "Empty Folder" for my junk mail folder after I take a quick glance to see if there is anything in there that I might want.