You need to disable the sync of email to CRM, wherever you have it. That's the only way to prevent the emails from getting pushed through.
If you're asking how to have the email only show on the Order and not the parent Account, then you need to change the view for Activities from "Related Records" to "Only This Record" on the Account. That will make sure emails on
the Order will not show up on the Account by default. The relationship will still be there, but the view filter is much narrower.
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