The main reason why your Orcon email address may keep downloading previously deleted emails to your mail client is that you are using POP3 with the option to leave a copy of email on the server selected.
POP3 copies emails from the server and downloads them to your local mail client. In most mail clients there is an option to leave a copy of the mail server. If you download an email to your client and delete it while this option is selected, the copy left on the server will download again the next time you open your client.
To avoid this happening, you can either set your mailbox up to use the IMAP protocol, or uncheck the option to “Leave a copy of my mail on the server”. IMAP is much better for managing email across multiple devices, so change your email now so that you can have access to your email always.