Resolving duplicate sent emails in outlook on a Mac

Dear community,

I'm trying to resolve the 'duplicate email in sent folder' challenge on a MacBook.  I've Read the various suggestions including the guidance of:

On the Tools menu, select Accounts…

Choose the affected IMAP account and select the Advanced… button.

Select the Folders tab

Select the radio button Don’t store a copy of sent messages

Choose OK

But this isn't working as the 3 options after clicking on 'advanced' are Server, Delegates & Security (no sign of folders).  Any ideas?

Thank you!