Polymail
Airmail
Spark Mail
Mailbird
Thunderbird
Canary Mail
Apple Mail
eM Client
Followup.cc
FollowUpThen
Gmelius
Boomerang for Gmail
Right Inbox
Onesheet CRM
SendRecurring
Mailbutler
Polymail Followup.ccFollowup.cc might be a bit more popular than Polymail. We know about 1 link to it since March 2021 and only 1 link to Polymail. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Polymail - This one is a lot like Twobird but with a lot more features. It's a different type of email client. It's really cool, but the Windows version is just a web app. It's available on iOS as well. Source: over 2 years ago
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
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
FollowUpThen - The simplest way to schedule an email reminder
Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues
Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
Boomerang for Gmail - Boomerang for Gmail is a Firefox / Chrome plugin that lets you take control of when you send and receive email messages.