There's not a way to subscribe to it, though it's not obvious how a subscription would work. The summary of any given day is not finished at the end of the day. Rather, the set of articles for that day, their summaries, and the articles themselves will all continue to grow as more information is gathered. So, it is a good way to "catch up" after some time away from current events. But to my knowledge there's no coordinated effort to "finish" a day or a month by any deadline.
I'd be glad if you could provide me with the link to subscribe these summaries if they're email newsletters. I could not find them in the wiki itself.