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I'll update this if I find more. For now, this seems to be a partial solution. It's a Gmail add on (except I don't use Gmail) that adds reminders. The options when setting reminders include cancelling it if someone replies, and to remind everyone in the thread. If you combine those two, it seems like — if you use Gmail's web client and have $23/month you're dying to get rid of — a decent way to add the feature. Source: over 1 year ago
FollowUpThen - The simplest way to schedule an email reminder
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Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.
Hmu - Hmu is a social app by SC Friends that enables users to search for new friends by viewing a list of users from all around the globe and tap on the desired profile to engage in live chat with them.
Right Inbox - Schedule Emails in Gmail To Be Sent Later
Flashlight - Control your Mac with a keystroke.