Tips that work in most cultures: assume the person is busy, not ignoring you; do not mention that tracking showed an open; give a clear question with a simple yes or no, or offer two time slots; and stop after two or three polite follow-ups.
Safe Follow-up offers a professional, concise or warm tone and does not create a draft when the person already replied, unsubscribed or the address bounced. It never sends anything on its own. On the Pro plan you can use reminders, which tell you when it is time to follow up.