That is very strange. I have seen this before, sometimes emails do get lost in the void of email processes. This particular email seems to have been sent out, and received a notice that everything was okay from your email service provider. Perhaps check your spam folder for the message. Be sure to mark Creative COW email as important and not spam to help them get to your inbox. Your email provider may have dropped the email somewhere in its system, as it looks like our mail system handed it off with a confirmation that everything was okay.
To check for posts which you have been emailed about, you can try in your messages list. Go to https://my.creativecow.net/ then click on the messages link right above your feed. This should show you posts which you were emailed about, but may have not received an email.
I know that this is obvious, but I don’t know if you’ve tried this two-step process: creating a filter for the creativecow.net domain, and if your email client permits, moving it to the place in the stack where it gets read first. (Some clients that’s the top of the list. Others it’s the bottom.) It tends to be the default that new filters are read first, but it’s worth checking.
The email did exist until it was sent to Gmail. I’ve tracked these emails and they are sent to Gmail and then they disappear. They did exist; Gmail is simply choosing to drop some of the email. There’s nothing we can do about that on our end, except for us to send less email, which isn’t really an option for us.