Unable to receive emails at cox.net from one source.

I think this problem is solved. I found the missing emails in my Spam folder although I have no idea why they started going there. I should have read past forum entries which put me on the right track. Thanks everyone.

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I have a family member in Florida with whom I've been corresponding by email for years. He uses tampabay.rr.com and I use cox.net. As of about a week ago none of his emails to me show up in my cox email inbox. Through testing (while talking on the telephone) we've determined that my email FROM cox.net TO him at tampabay.rr.com arrives just fine. The problem occurs ONLY when he sends email to me. As a further test I had him send an email (from tampabay.rr.com) to a friend who also uses cox.net. The friend also did not receive the email. So the problem appears to be that cox does not receive emails from tampabay.rr.com. My family member can send emails from tampabay.rr.com to other (not cox.net) email addresses and they arrive fine.There are no error messages on either end, it's as if the emails just disappear into outer space..

Does anyone know how I can isolate this problem to to the sender (tampabay.rr.com) or the receiver (cox.net)?

Thanks for any suggestions.