Cannot send from behind NAT with private IP

  • Resolved eitanc

    (@eitanc)


    1 year ago

    Hello,

    Post SMTP is installed on a backend server with only private IP, which connects to a gateway that is a Firewall, which holds the public IP that sends the email, using 1:1 NAT with the above server.

    My problem is that the relay server is configured to accept outbound emails only from the public NAT IP of the FW (and cannot be set to accept from private IPs), but the plugin sends the email using the private IP, hence being rejected from sending by the relay server.

    It sends:
    “
    250-Server-FQDN Hello Sending-Domain-Name [the-numeric-private-ip]
    “

    Is there a way to control the IP used by the Hello command? either set it manually or let the plugin check what is the actual public IP and then use it?

Viewing 2 replies - 1 through 2 (of 2 total)
  • Thread Starter eitanc

    (@eitanc)

    OK, I solved it.

    My cPanel server kept sending me emails after each failed test delivery, so I realized that emails probably were not being sent directly to the relay server that I set in the plugin’s setting, but first needs to pass the local email server, Exim, which is the one actually blocking and replying with the error message to the plugin.

    This also fit nice with the fact that I didn’t see any fw logs for any email delivery test by the plugin…

    Solving this was by going to cPanel’s WHM admin site and going to – Service Configuration > Exim Configuration Manager > Access Lists > the line of “Trusted SMTP IP addresses” > click its matching “Edit” button > adding to the list the IP of the local server (the on that shows in the plugin’s error message) > Click “Save” for the list pop-up window > click “Save” for the overall “Exim Configuration Manager”

    I think it will be good to add a note in the settings page, for each selected mailer type – to be clear which system/server is the one to be first in the delivery chain, which may be different from the value we have set in the field of “Outgoing Mail Server Hostname”, this will make things more clear.

    Thanks.

    Plugin Support M Haseeb

    (@haseeb0001)

    Hi @eitanc

    I hope you are doing well.

    Thank you for reaching out, and I’m delighted to hear that your issue has been successfully resolved.

    Your detailed feedback and guidance are much appreciated. If you ever require assistance in the future, please don’t hesitate to reach out to us anytime.

    Thanks and regards,
    Support Team – WPExperts??

Viewing 2 replies - 1 through 2 (of 2 total)
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