I can send messages to the subject person, but can't receive his replies. This happens only with this one person, so I suspect his IP address is being blocked by TW / Spectrum. How can I confirm this? I know the sender's IP address.
One place that I have found to be very useful in these circumstances:
Hope this helps find the information you are looking for.
Thank you for your participation in the forums.
Spectrum-Social Media Customer Care
Lead Moderator-Community Forums
I am also having this problem with several of my emails sent from even very large companies. Just not receiving the emails that they send to my TW email account. Can receive them just fine to my work account. What exactly is the mxtoolbox tool telling me? if it does show errors, then what? How do I get this fixed? Seems to be happening more and more.