Postfix internal allow relay for internal host

Alexandre Takacs
Alexandre Takacs used Ask the Experts™
Probably a basic one but can figure it out.
I am setting up a Postfix server to accept mail form our LAN and relay it to external WAN.

Mail sent from the LAN devices (MFC etc) get this error:

Remote Server returned '554 5.7.1 Client host rejected: cannot find your hostname, []' is indeed the correct LAN IP. How do I authorize it ?
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David FavorFractional CTO
Distinguished Expert 2018

Commented: provides all private/local/non-routable IP address ranges.

The address you're using will never receive packet flow from outside your LAN, as you're using a 172.16.X.X address.

If I understand your question, you'll require using a public IP.
Software Engineer
Distinguished Expert 2018
This error is about missing reverse lookup. You can add your LAN IP's as reverse lookup.
Also you can accept mail using:

    # Allow connections from trusted networks only.
    smtpd_client_restrictions = permit_mynetworks, reject

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Permit the request when the client IP address matches any network or network address listed in $mynetworks.

Maybe start here with reading:

The serup you are looking for is a so called "smarthost" setup.


Thanks - I am indeed looking into setting up a "smarthost" and had to "white list" the relevant internal subnets in the mynetworks directive of the postfix server. Seems all ok now !

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