Since 9/8 Monday afternoon, we are no longer receiving emails from homedepot.com. We usually get 12-24 a day b/c we are one of their vendors. No Exchange changes have been made from our end.. Our emails are being received by Home Depot, but we cannot receive their reply emails.
I have troubleshooted this issue with both Symantec, Dell SonicWall and 1 & 1 Internet and they had confirmed they are NOT blocking any emails. I looked at the Exchange logs and it appears that none of their emails are even hitting our MX record any more. I tried pinging their MX record address that we used to receive from and I get no response.
It's been over 72 hours and I don't think it is a simple propagation issue.
How can I check to see why emails are getting blocked from just one customer of ours? We do send and receive all other emails from everyone else.