Several people are reporting an increase in emails from JC after last weekend's migration. It happened to three of my accounts, and Kim England and Russell pearson (oddly all UK-based). In addition your timezone may have reset.
If you are getting this behavior (or behaviour in UK), you need to go to the dropdown top right, then Preferences > General Preferences and reset any that are now 'on' to 'off' - for example People, places and content I'm following (Followed Activity)
Ryan Rutan is investigating. Apologies to other people whose threads or cases got taken off-topic by us talking about this issue - but I have created this doc prior to Ryan responding.