Hello,
I'm using Proxmox Mail Gateway in front of an internal mail server (WHM/cPanel) to manage email sending and receiving.
Everything works fine for inbound mail. The problem is when sending outbound emails from my internal server to any external domain (e.g., Gmail, Hotmail, company.com). The following error appears in the logs or via telnet
The issue:
It's practically impossible to pre-add every external domain, as I support many clients reaching hundreds of destinations.
My questions:
Any help, official solution, or recommendation is appreciated.
I'm using Proxmox Mail Gateway in front of an internal mail server (WHM/cPanel) to manage email sending and receiving.
Everything works fine for inbound mail. The problem is when sending outbound emails from my internal server to any external domain (e.g., Gmail, Hotmail, company.com). The following error appears in the logs or via telnet
- have added my mail servers/networks to the PMG trusted networks section.
- I reviewed main.cf and postconf to ensure:
- mynetworks includes my mail server IPs/networks.
- smtpd_recipient_restrictions starts with permit_mynetworks, followed by reject_unauth_destination.
- Testing sending via telnet from the internal mail server to PMG shows the same error unless I manually add the target external domain to PMG's Relay Domains.
- When I add the external domain to Relay Domains, sending succeeds.
The issue:
It's practically impossible to pre-add every external domain, as I support many clients reaching hundreds of destinations.
My questions:
- Is there an official way or option in PMG to allow trusted networks to relay email to any external domain, without manually populating Relay Domains?
- Is this a security policy by design, with no workaround except heavy customization or forwarding through an external SMTP relay?
Any help, official solution, or recommendation is appreciated.