Getting rid of localhost from email header

Question

Getting rid of localhost from email header

6.3k Views Asked by trix87 At 13 April 2025 at 14:03

I am running an ispconfig web/mail server on server1.fvdevelopment.com and the problem is that my mail ends up in spam at Google. I have everything set up rDNS, DKIM, SPF, dmarc, tested it on mail.tester.com and got 10/10 so I don't think that the record part would be an issue. However, my mail header contains at one place localhost. According to Google it's a bad practice.

The header would be as follows:

Received-SPF: pass (google.com: domain of [email protected] designates 207.154.236.132 as permitted sender) client-ip=207.154.236.132;
To: [email protected]
Subject: Friss hirek jöttek
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Date: Thu, 05 Oct 2017 10:44:10 +0200
From: "Mag Norbert Fotográfus" <[email protected]>
Message-ID: <[email protected]>
User-Agent: Roundcube Webmail/1.2-beta

As you see there is a localhost at the "recieved from" part. My /etc/hosts looks as follows:

207.154.236.132 server1.fvdevelopment.com
127.0.0.1 server1.fvdevelopment.com server1
127.0.1.1 server1.fvdevelopment.com server1
127.0.0.1 localhost.localdomain localhost

My /etc/hostname has server1.fvdevelopment.com.

Any ideas on how to get rid of that localhost part because I tried an awful lot of variations but can't get rid of it.

Best regards, Trix

Original Q&A

There are 3 best solutions below

**Eddie Kaka Svensson** · Answer 1

Just remember ^^ If you change something in the Global Filters in Ispconfig then all your manually edited regexes will disapear from /etc/postfix/header_checks

I've just added those fields directly under Email -> Content Filter

Best regards

**Leo K** · Answer 2

The mail headers in your log indicate that the message is forwarded internally on your host once or twice before it is sent out to gmail. I don't know what the internal server setup is, but it seems that 'postfix' is sending it to itself (or to a different instance of itself) internally before it goes out. On one of those 'hops', the sender is being detected or reported as 'localhost'.

To avoid this, do the following: - modify /etc/hosts not to have the same IP address for localhost and for your actual server name, e.g., try this:

207.154.236.132 server1.fvdevelopment.com
127.0.1.1 server1.fvdevelopment.com server1
127.0.0.1 localhost.localdomain localhost

(note the 'external' name is NOT on 127.0.0.1)

check all config files related to the mail service for any references to 'localhost' and kill them (replace with the server name).
check all config files related to the mail service for any references to the IP address 127.0.0.1 and change them to 127.0.1.1. That way, a connection from the host to itself for the 'internal hop' will still be on the lo interface, but NOT on 127.0.0.1, so it will not have a chance to be back-resolved to localhost.
verify that the chosen secondary local address (e.g., 127.0.1.1) back-resolves to your full server name (e.g., python -c 'import socket as s ; print (s.gethostbyaddr("127.0.1.1"))'
verify that hostname --fqdn returns server1.fvdevelopment.com (this would normally be the case if your hostname is set to server1).

**nbari** · Answer 3

Check the smtp_header_checks option, for example in main.cf add this line:

smtp_header_checks = pcre:/usr/local/etc/postfix/header_checks.pcre

And in /usr/local/etc/postfix/header_checks.pcre you could use the following to hide some extra headers besides the ones starting with Received: like the User-Agent, sender IP or even the signature of RoundCube X-PHP-Originating-Script:

/^Received:/                  IGNORE
/^X-PHP-Originating-Script:/  IGNORE
/^X-Originating-IP:/          IGNORE
/^X-Mailer:/                  IGNORE
/^User-Agent:/                IGNORE

smtp_header_checks is applied only for outgoing mail (smtp client)

Getting rid of localhost from email header

There are 3 best solutions below

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