Postfix error "501 5.5.4 Invalid domain name"

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Postfix error "501 5.5.4 Invalid domain name"

SysAdmin EM
Hello,

I have two servers running on Postfix, one of which runs version 2.10.1 and the other server runs version 3.4.7.

On the server where I am running verion 3.4.7, I receive "501 5.5.4 Invalid domain name" errors in emails sent to different servers. Rhe mail is sent to postfix through exim from a relay connection.

The reverse of the IP is configured correctly and the From domain is also responding.

# Log example

postfix-out/smtp[12931]: E30639204ED: to=<[hidden email]>, relay=hotmail-com.olc.protection.outlook.com[104.47.124.33]:25, delay=1.4, delays=0.08/0/1.4/0, dsn=5.5.4, status=bounced (host hotmail-com.olc.protection.outlook.com[104.47.124.33] refused to talk to me: 501 5.5.4 Invalid domain name [HK2APC01FT037.eop-APC01.prod.protection.outlook.com])

The only difference that I see in the logs of version 2 and version 3, is the following

# Postfix 2

postfix/smtpd[2377]: 539628047FD1: client=servername[179.x.x.x]

# Postfix 3

postfix-out/smtpd[9433]: 7F6809204ED: client=localhost[127.0.0.1]

Any ideas?

Regards,

Any ideas?
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Re: Postfix error "501 5.5.4 Invalid domain name"

Viktor Dukhovni
On Thu, May 14, 2020 at 09:07:29AM -0300, SysAdmin EM wrote:

> postfix-out/smtp[12931]: E30639204ED: to=<[hidden email]>,
> relay=hotmail-com.olc.protection.outlook.com[104.47.124.33]:25,
> delay=1.4, delays=0.08/0/1.4/0, dsn=5.5.4, status=bounced
> (host hotmail-com.olc.protection.outlook.com[104.47.124.33]
> refused to talk to me: 501 5.5.4 Invalid domain name
> [HK2APC01FT037.eop-APC01.prod.protection.outlook.com])

The "refused to talk me" prefix means that the delivery attempt was
rejected either in the server's SMTP greeting or the EHLO response,
however the actual response also contains a 5.5.4 DSN status code,
which would only be appropriate in response to EHLO.  Therefore,
the pattern was:

    C -> S: TCP SYN
    S -> C: TCP SYN ACK
    C -> S: ACK
    S -> C: 220 <server-hostnname> ESMTP ... <CRLF>
    C -> S: EHLO <your-hostname> <CRLF>
    S -> C: 501 5.5.4 Invalid domain name <CRLF>

The 501 code suggests a syntax issue, from which it seems that Microsoft
are claiming that your SMTP EHLO name is malformed.

Therefore, take a close look at your "smtp_helo_name" and "myhostname"
settings.

--
    Viktor.
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Re: Postfix error "501 5.5.4 Invalid domain name"

Matus UHLAR - fantomas
In reply to this post by SysAdmin EM
On 14.05.20 09:07, SysAdmin EM wrote:

>I have two servers running on Postfix, one of which runs version 2.10.1 and
>the other server runs version 3.4.7.
>
>On the server where I am running verion 3.4.7, I receive "501 5.5.4 Invalid
>domain name" errors in emails sent to different servers. Rhe mail is sent
>to postfix through exim from a relay connection.
>
>The reverse of the IP is configured correctly and the From domain is also
>responding.
>
># Log example
>
>postfix-out/smtp[12931]: E30639204ED: to=<[hidden email]>, relay=
>hotmail-com.olc.protection.outlook.com[104.47.124.33]:25, delay=1.4,
>delays=0.08/0/1.4/0, dsn=5.5.4, status=bounced (host
>hotmail-com.olc.protection.outlook.com[104.47.124.33] refused to talk to
>me: 501 5.5.4 Invalid domain name [
>HK2APC01FT037.eop-APC01.prod.protection.outlook.com])

is your hostname really "HK2APC01FT037.eop-APC01.prod.protection.outlook.com"?

--
Matus UHLAR - fantomas, [hidden email] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
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