We deal with a lot of automated email messaging systems. These systems are all usually capable of sending email, but not easily managing opt out requests. It seems to me that it would be a good feature to have, if you had a a mail account that is being used to send email keep track of who the emails are being sent to, and then if someone replies back with a Opt Out request that it track it inside a Opt Out Contacts list. The idea is to simply stop that email account from sending future emails to someone who has opted out and instead place it in the trash. This would allow automated systems that send email, to send through mdaemon, and mdaemon would not send emails when there was a contact in Opt Out. This is not the same as a mailing list, because it would allow individual emails and messages to be sent to anyone, but still give them the ability to Opt Out whenever necessary and no person would have to manually update or remove their address for the messaging / alert systems.