If you open the email properties, you can actually see when it was sent AND delivered. Not all email issues are on the Cox Side. I had a verification email from my financial institution come 2 hours late, and when I checked the header information, I found that it was sent 20 seconds before i received it, the problem was actually on the sender's side.
Additionally, it's interesting to note, that IAW RFC specifications for email, delivery should be within 24 hours of being sent, however retries can take up to 4 or 5 days IAW RFC 5321, so the idea that they are sending you an email that's only good for 10 or 15 minutes is ludicrous.