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SMTP relaying depending of the recipient #1470

@cottonthread

Description

@cottonthread

Context

I created an home server with my Non-rDNS IP for my garage company (a startup without any financing and during COVID-19, yeah! 🥇 ), now I see I can't delivery any mail to those servers which need to verify rDNS records. Like mx01.1and1.es or kundenserver.de... It always deferrer my messages without any communication to my email inbox, the only way to detect it is based on the daily informing or looking into real-time server logs.

I found out some solutions to have a rDNS record like SendGrid, but for freemium, only 100 messages per day could be offered, and that is not enough, because all of our partners needs this quota. And I don't think creating multiple SendGrid account is an ethical ideal.

Expected Behavior

Maybe there is someway which allow me use the relay server just in case of recipient's domain.

Actual Behavior

Right now like in the Repo Wiki says, it just allow us to use SENDER relay: here

Possible Fix

Maybe this is the solution?
https://www.linuxbabe.com/mail-server/postfix-transport-map-relay-map-flexible-email-delivery/amp
http://www.postfix.org/transport.5.html

I think transport_maps and relay_transport is the key. But I really don't have the technical skill to follow and execute the process included in the link.

Steps to Reproduce

  1. Send an email located in mx01.1and1.es or kundenserver.de, I am sorry for could not provide any email address due to the privacy issue.

Your Environment

  • Any relevant stack traces ("Full trace" preferred):

Apr 24 11:46:44 MYHOST postfix/smtp[25410]: 6CAE65D007: host mx01.1and1.es[217.72.192.67] refused to talk to me:
554-kundenserver.de (mxeue109) Nemesis ESMTP Service not available 554-No SMTP service 554-Bad DNS PTR resource record. 554 For explanation visit https://www.ionos.com/help/index.php?id=2425&ip=0.0.0.0&c=rdns

Thank you for creating such magnifical docker so people like us can use it easily. I hope to get your kindly help for solving this issue and maybe it can help other people too! 👍

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