Thank you for your question. Our spam filter blocks incoming email from blacklisted IP address, and your yahoo mail IP (18.104.22.168) is currently listed on several blacklists, as can be seen here:
I was able to determine this IP address is owned by Yahoo, by performing a Whois lookup
Here is a link to our guide that explains why Why mail servers get blacklisted.
UnfortunateIy, we cannot change the IP since it is not owned by us. I recommend forwarding this bounce message to Yahoo, so they can request removal from the blacklists.
If you have any further questions, feel free to post them below.
Like this Question? Tweet