devadi_dev
I assume you have "Do nothing (not recommended)" set for your Fetched Emails setting for the system email (Admin Panel > Emails > Emails > click the email being fetched from > Remote Mailbox > Fetched Emails). As the option states, this is not recommended. If you "do nothing" the emails remain in the inbox and have a chance of being reprocessed. Although the Message ID of that email should remain in the ost_thread_entry_email table so it shouldn't recreate a ticket unless that record got deleted somehow (this should not happen on normal ticket delete process - see here) or somehow magically the Message ID of the email got changed (which I highly doubt). You can instead change the Fetched Emails option to "Archive - Move to folder" which will move the emails to a separate folder after fetching or change it to "Delete emails" where it will delete the emails after fetching.
Please note that if you go with either option it will go through the configured Fetch Folder (every single email in there) and reprocess them which means attempt to recreate tickets if they don't already exist. So what I recommend is moving all previous emails out of the configured Fetch Folder into a separate folder first (or delete them) then change your Fetched Emails setting. This way the system only sees and processes the new mail and you won’t run into chaos.
Cheers.