Windows 12? I'm guessing that you mean Windows 10 but that doesn't really help me understand your question anyway because (any version of) Windows is an operating system, not a means of accessing emails.
So I'm guessing that you're using the email app that Windows 10 comes with (rather than a third-party email client, such as Thunderbird, or web-based email) but it would be nice to have that confirmed.
If so, how are you deleting your emails? (Are you opening them and then clicking on 'Delete' or are you deleting some unopened).
Further, how are you receiving your emails? (Is it as POP3 account or an IMAP one?). If, as I suspect, you're using IMAP, then it seems likely that your sync settings are configured in a way that doesn't suit your needs,. (i.e. you're only deleting emails locally on your computer, not on the host server, so they're reappearing later on when the account is re-synced).
Information, please!