Whenever something is update on a software development platform, usually an email is sent to all subscribed users. Phabricator let you reply to those emails and perform a specific action like assign, claim, close, change priority and status, unsubscribe, etc. In order for this to function with a local MTA like Postfix, a manual setup must be done.
Let’s Encrypt is a free, automated, and open Certificate Authority. Recently the automatic SSL certificate renewal request for one of my domains, which is in instance of Phabricator, was about to happen but an error occured. The problem was not with Let’s Encrypt, but with the way this domain was configured.