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These are just display names of your autocomplete entries. They can have any style of address of don't have the email at all. You can't change this in Outlook: it just stores entries "as is" from the emails you're using in your replies, etc.
But you can edit your autocomplete cache with one of the free utilities available.
Different countries have different names for all these brackets, so I edited to broaden the audience. To a Brit, the original made little sense without the picture ;) – Tetsujin – 2018-07-11T15:58:29.100
These are just autocomplete caches, what if we delete one of the entries by clicking 'X' next to it, and then recreate the list? Will it display the same angle/chevron brackets? – Steve Fan – 2018-07-12T06:27:50.890