Google Apps for ISPs is gone
Google Apps for ISPs is being shut down. While this was a scheduled end of life, apparently some users weren’t notified (always keep the contact email address up to date at your vendor!) and other users were told that it would be discontinued in July and were surprised when their service was turned off a month earlier than they expected.
I’ve not seen any reports of mail bouncing due to this yet, but it’s likely that some consumer ISPs will be scrambling to migrate to new email providers and their inbound mail may be a mess for a while. If you see domain-wide problems at consumer domains, check to see if their MXes point at the google aspmx cluster.
It seems to be a rolling shutdown, and some ISPs have apparently had their service extended by a few days or weeks, so issues may start with some domains throughout the month.