I understand in theory how and why opens/clicks are not tracked with text emails, but when I run an email performance report it is showing opens. How does that work?
Are you sending an email with only a text part?
Have you actually wrapped links with [[square brackets]] so they are, in fact, rewritten and tracked?
You may also want to read this: Add Tracked Links to a Text Email - Marketo Docs - Product Docs
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