Unable to receive emails from specific email address/domain

Hello all,

I'm trying to troubleshoot an odd issue regarding emails sent by team******@tdx.charlotte.edu. Based on my testing, emails sent by this address are not received any @icloud.com addresses. However, this address is able to send emails to @gmail.com, @yahoo.com, and other mail providers without issue. I have tested this issue with multiple iCloud email addresses and it seems to be a universal issue with those accounts.

For additional context, I am not the owner or operator of the address. I just noticed that there were delivery issues to my address and started to investigate. This same issue also happens with a different email address of mine that I set up to use a custom domain. That issue seems to be caused by tdx.charlotte.edu missing A, AAAA, and MX DNS records. I am trying to determine if this issue is a result of those same missing records. Both issues strike me as odd because mail delivery happens without issue to most other mail providers I have tested, so they must be validating the mail using some method besides DNS records.

Any information or ideas that people could provided would be greatly appreciated.

[Edited by Moderator]