Postfix gives me “Sender address rejected: need fully-qualified address;” errors with what looks like strange addresses

email-bouncesemail-serverpostfixubuntu-16.04

I am receiving some error messages like this:

Jan 28 17:20:47 halk postfix/smtpd[29413]: NOQUEUE:
    reject: RCPT from mail.m2osw.com[138.197.205.139]:
    504 5.5.2 <SRS1=R3xB=m2osw.com==hj4N=ZL=lime.ocn.ne.jp=@com>:
    Sender address rejected: need fully-qualified address;
    from=<SRS1=R3xB=m2osw.com==hj4N=ZL=lime.ocn.ne.jp=@com>
    to=<secret@valid.domain.tld> proto=ESMTP helo=<m2osw.com>

I'm not too sure I understand the "email" address found between the angle brackets:

SRS1=R3xB=m2osw.com==hj4N=ZL=lime.ocn.ne.jp=@com

That looks like crap to me, but maybe it's a form of envelop?

The original From looks like this:

From: western union <"westernunion1."@lime.ocn.ne.jp>

(which is a clear spam email, but that happens with non-spam as well.)

As far as I know my setup worked fine before, but I upgraded one of my mail servers to the newest postfix (well Ubuntu 16.04 instead of 14.04). The archive server was upgraded a while back.

This error happens when I send myself an email from gmail. Then gmail receives a bounce.

The setup is something like this:

+------------------+    +------------------+
|                  |    |                  |
| Client           |--->| Main Server      |
|                  |    |                  |
+------------------+    +------------------+
                                |
                                v
                        +------------------+
                        |                  |
                        | Archive Server   |
                        |                  |
                        +------------------+

On the Main Server, the email works as expected. The error occurs when the email reaches the Archive Server.

Is there something that could have changed that "breaks" the email address in such a way when forwarding from one postfix MTA to another?

Best Answer

I don't think so, the log that you shared shows that everything looks OK and postfix working good. If you need to have more information about what is going on, add the following to main.cf:

error_notice_recipient = postmaster@yourdom.com
delay_notice_recipient = $error_notice_recipient
bounce_notice_recipient = $error_notice_recipient
2bounce_notice_recipient = $error_notice_recipient
#The list of error classes that are reported to the postmaster
notify_classes = bounce, delay, policy, protocol, resource, software

The rejection is because one of these lines:

reject_non_fqdn_helo_hostname,
reject_non_fqdn_recipient

I hope this helps

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