@GMHDI , interesting that it's creating copies.
I'm having an issue (which I emailed a video to MacRumors, will see if they post) where the badge icon says I have 1,000+ unread emails, I open Mail (which defaults to unread mailbox) and see like 3 messages. It will constantly cycle through "downloading 3 messages, downloading 5 messages, downloading 2 messages, etc." with random numbers (usually <10 at a time) with the status bar progressing, then disappearing, then reappearing with the next downloading messages notice.
If I delete an email, it will reduce the unread badge count by several hundred at a time. Deleted emails in this instance will reappear.
When I get home and use my iMac or MacBook, I will see the message again (even if it was previously deleted on my iPhone). If I delete it on my Mac, I'm often asked "are you sure you want to delete 3,355 messages?" or something similar with one email being reported as several thousand emails. Sometimes macOS Mail will crash from all this.
One thing that I do have is numerous rules to highlight certain messages (financial institutions green, work red, daughter's school pink, etc.). I also have a few rules to make sure that some emails are never put in the junk folder. I was getting "unable to move to inbox" errors with MIME codes. I turned off all rules tonight to see if it helps.
Like others, I too frequently delete an email on my iPhone only to have it reappear and require that I hit the delete button again.
iOS 13 seems like it's in alpha testing and not ready for production. I feel like it was rushed without quality testing or at least paying attention to feedback received.