Cannot receive messages from nine.testrun.org as of 12p UTC 20251210

Mutual Help
1

As of 12p UTC, unable to receive messages from nine.testrun.org. After submitting a ticket with email provider, they showed that nine.testrun.org changed IPs today and they don’t think anything changed on their end. Is it possible there was a configuration error with changes today?

Delta Chat version

Flatpak Desktop 2.25.3 on Linux and various mobile devices

Expected behavior

Traditional email address user on DeltaChat to receive messages from users on nine.testrun.org

Actual behavior

Between 11a-12p UTC, traditional email server stopped receiving messages from nine.testrun.org and now responding to users on nine.testrun.org with this message:
Dec 10 10:25:54 email postfix/smtpd[2844933]: NOQUEUE: reject: RCPT from static.147.132.181.135.clients.your-server.de[135.181.132.147]: 554 5.7.1 : Client host rejected: Generic - Please relay via ISP (your-server.de); from=@nine.testrun.org to= proto=ESMTP helo=

Steps to reproduce the problem

  1. Send message to traditional email server from nine.testrun.org
  2. Observe error message in red error circle on message sent

Debug logs

Behavior that worked before 12p UTC today Dec 10 03:05:03 email amavis[2603405]: (2603405-10) Passed UNCHECKED-ENCRYPTED {RelayedInbound}, [116.202.233.236]:47736 [116.202.233.236] ESMTP/ESMTP @nine.testrun.org -> , (ESMTPS://[116.202.233.236]:47736), Queue-ID: 4dRCYC1PpDz97Rc, Message-ID: , mail_id: 0cWL40G01-K, b: 7nFi17u8, Hits: -, size: 3860, queued_as: 4dRCYC3Hq2z97Rg, Subject: "[…]", From: @nine.testrun.org (dkim:AUTHOR), helo=nine.testrun.org, dkim_i=@nine.testrun.org, dkim_sd=opendkim:nine.testrun.org, 171 ms
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2

PTR record was not set correctly for the new IP address, but it is correct now, 147.132.181.135.in-addr.arpa. resolves to nine.testrun.org.

In any case, looking at PTR records is not a way to authenticate email servers, this is a misconfiguration of postfix on your email provider side. Would be great if they can get rid of it. This does not protect against anything because anyone can set PTR record for their IP address to any hostname, this option exists in Postfix only for historical reason, because Postfix is written by the author of TCP Wrappers: draft-ietf-dnsop-reverse-mapping-considerations-06

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