Would be great.
Caveat is - significant number of people simply don't really read emails (even if they have 3-5 sentences) 
https://twitter.com/Rockstox/status/1235537913183535105 …
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Superhuman seems to do the trick. Read receipts may be considered privacy concern, but CMD+H (remind me if no reply until <date>) is in itself worth a lot
There's no privacy concern in a work environment, though. For certain communications, I think you can be contractually obliged to acknowledge you've read them...