Same here, last 3 sales have not had an email come through.  This is about the third period of time this has happened this year.

My theory is that their emails are being blocked by either outgoing or incoming server spam filters which have had updated software from Cisco which have a monopoly over this industry, as I've had a lot of email delivery problems this year due to over-enthusiastic filtering of order-related emails.  It can take months for Cisco to fix problems from individual requests, but I imagine they'd work faster for PayPal.

My theory is backed up by the fact that their email formatting has changed several times over the past few weeks, from pretty HTML changes to becoming simple and messy line-by-line layouts.  I don't like the new format, it's very messy to try and read.  But changing the format several times is what I had to do as a web developer to work with Cisco's filters.