Slack – How to Automatically Set Yourself to Away

• Create a Gmail account, and a Facebook account for it.
• Join the Facebook group with it.
• Configure it to receive all email notifications from the Facebook group.
• Create a Gmail filter that forwards to the mailing list all emails from the Facebook address that sends email notifications (e.g., notification+zj4zg6a944oc@facebookmail.com).

If you use Google Groups for the mailing list then in order to verify the Google Groups' address for auto-forwarding, you'll have to temporarily configure Google Groups so that the public can post to it.

The only problem with this solution is that Facebook currently only sends email notifications of comments on posts if you've commented on the post or if you're tagged in it, so unless you comment on a post (Facebook allows you to do this through email), the mailing list won't receive forwarded notifications of any other comments on that post.

Using the Trello API, I created a bot that can do exactly what you want (and a lot more). It's been running for a while with very satisfied users (see this reddit thread).

To use it, you invite user "butlerbot" to your board. It will create a list called "Butler" automatically. You enter commands as cards in that list.

The command you want is something like:

on a card's due date, move it to list "Inbox"

This command will move the card at midnight the day it's due. If you prefer a different time, you can specify it:

on a card's due date at 8pm, move it to list "Inbox"

(You may want to set your timezone if you're not in US eastern time, there's a simple command for that too.)

Another alternative:

the day after a card is due, move it to list "Inbox"

This will move it to the list the midnight after its due date.

If you need help using it, there's a public Trello board. The developer (that would be me) is very responsive.