I use Outlook 2016 for all my email requirements.

One BTinternet.com email address
One Outlook.com email address

Previously had above two email accounts sending and receiving from the same PST file each using POP3.

Wanted to change the Outlook.com to IMAP with my understanding being that this would then sync both ways with the web-mail for Outlook.com.

Deleted the old POP3 account settings for the Outlook.com email address and then went through the process of setting up again using the automatic configuration rather than the "manually configure" thinking this would automatically use IMAP. (Left settings unchanged for the POP3 BTinternet.com email address).

To my surprise the Outlook.com email address was not setup as an IMAP but as an Exchange Server.

Initially thought this would be ok as this would also sync both ways with web-mail. Soon discovered however that any email coming in to my still remaining BTinternet POP3 email address was also arriving into the Outlook.com Inbox.

Why is this happening and what do I have to do to still keep the POP3 email separate from the Exchange Server email each using their own Inbox? (Both Inbox's are listed in the left hand panel of Outlook 2016).

Any help much appreciated.