Outlook 2018 has many annoying bugs, but luckily KM is almost always the answer for everything.
E.g., when you see an email address as a recipient or sender, and copy it to the clipboard, Outlook redundantly copies it as
someone@something.com <someone@something.com>
This macro will detect this format, and convert it to only
someone@something.com
The macro is safe universally, but you may want to import it into a group only available in Outlook. Hope this is helpful to someone.