We just started having problems emailing a company we work with and
regularly exchange emails with. In the GWIA logs I'm seeing
"deferring message" and "420 TCP write error". I looked up their
domain (brooks1st.com) at mxtoolbox.com. I see two hostnames listed.
The one with Preference 10 says no A record. The one with Preference
100 does have an A record. That doesn't seem right. Is that the
issue here or do I need to be looking for something on my end?