From time to time it occurs that two people answer a mail in the same way where one would do – closing an unblock request, for example.
When this almost happened on debian-release the other day I amused myself by dreaming up an SMTP header that would prevent such embarrassment. I wasn’t being serious in the slightest, but nevertheless X-RaceProtection was born (and it turns out at least one resident of a certain IRC channel thought I was).
X-RaceProtection can be a message identifier or the simple value ‘yes’ and is intended to prevent duplicate replies to, for example, mailing lists. When set as a mail ID, list software should silently drop the message being delivered if the identified message has already received a reply – that is, another message quoting that ID in In-Reply-To. If X-RaceProtection is simply ‘yes’, the mail ID of In-Reply-To for the message being delivered is used, providing a shortcut.
This means you can set X-RaceProtection when replying to a mail where there is a chance of collision. If someone beat you to it, there is no embarrassment at your mail arriving with a later timestamp.
If someone fancies implementing this for smartlist/debbugs, please be my guest!