A client cannot deliver to our PMG, he can ping our mail gateway, but nothing gets delivered, I checked the logs, his IP address yields no results. I can telnet his server on port 25.
Our PMG is hosted on Proxmox VE, so I disabled cluster & instance firewalls and white-listed his address in Postfix, then asked him to send another test message, still nothing. He tells me his company exchanges thousands of emails, but that from time to time this happens with other correspondents. He is running an old Exchange server on Windows server 2008. When he sends a message to me via gmail, it is received with a "Domain.com did not encrypt this message" indicating a lack of S/MIME usage.
Anyone know what's going on here & how we can get these messages delivered?
Our PMG is hosted on Proxmox VE, so I disabled cluster & instance firewalls and white-listed his address in Postfix, then asked him to send another test message, still nothing. He tells me his company exchanges thousands of emails, but that from time to time this happens with other correspondents. He is running an old Exchange server on Windows server 2008. When he sends a message to me via gmail, it is received with a "Domain.com did not encrypt this message" indicating a lack of S/MIME usage.
Anyone know what's going on here & how we can get these messages delivered?
