As a long time MAC user, I abandoned using MAC mail from OSX 10.6.
The only settings you need to have changed are - https://www.telstra.com.au/support/category/email/set-up/imap-pop-and-smtp-information-for-manual-email-set-up
Did you delete the old Microsoft mail settings, or did you change them or maybe you created a new mail profile. Hence maybe you have (2) profiles.
You say you have current version of OSX - what version do you have?