For like or dislike specifically, the cleanest read is a one-click feedback link at the bottom of each email, a thumbs up or down or a "was this helpful?" button where each option is its own tracked URL. That gives you direct sentiment on educational content without guessing. Opens are basically noise now since Apple inflates them, so I'd ignore those as a "like" signal.
Beyond that, watch the signals that actually mean something: click-through on the content itself, reply rate and what those replies say (for educational sends, replies and questions are the strongest sign it landed), plus the negative side, unsubscribes and spam complaints per send. Track it per segment and per email across the sequence, not blended, so you can see which topics resonate and whether engagement is climbing or decaying send over send. If a specific email spikes replies and clicks, that's your audience telling you what they want more of.
Best,
Floqal