[Feature Request] Modify List-Unsubscribe message header to forward through Addy

[httpjamesm]

Marketing emails have List-Unsubscribe headers that tell email clients where and what to send to unsubscribe from marketing lists. I'd like Addy to modify this so the recipient address for unsubscribing is a proxy address. This would allow unsubscribing using email clients without revealing your true address, as the unsubscribe message would go through Addy.