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postfix-users: RE: ..::Spoofing Issues::..

RE: ..::Spoofing Issues::..

From: Alfonso Alejandro Reyes Jimenez <aareyes_at_nospam>
Date: Mon Oct 04 2010 - 21:16:36 GMT
To: "mouss" <>, <>

Thanks for your help, right now we use sasl auth and Works very good.

If the setup for example a gmail account and the change the gmail address for some user on the postfix domain, postfix delivers that email.


I don't want to accept emails from our domain in our server if they don't belong to my networks or they are authenticated.


For example if you setup you outlook to send an email from using gmail as smtp relay, I want my postfix to drop that email because it is coming from other smtp server.


I hope this example helps.


Ing. Alfonso Alejandro Reyes Jiménez
          Analista del sector Gobierno
E-mail: <>
Telefono: 91 50 74 00 ext. 7489
Movil: (044) 55 52 98 34 82


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De: [] En nombre de mouss
Enviado el: lunes, 04 de octubre de 2010 03:48 p.m.
Asunto: Re: ..::Spoofing Issues::..


Le 04/10/2010 21:37, Alfonso Alejandro Reyes Jimenez a écrit :

Hi, everyone.


I have an issue with some users that are spoofing our mail server, rightnow we can restrict the spoofing on the same server.

But if they use another smtp server pretending that they are on our domain the can send those emails.

That's a FEATURE in smtp...


I use to work with websense which can be configured to get only mails from the users and ip address that belong to the domain, is there some way to tell postfix that he owns the domain and it reject everything that pretend to be the same domain?


Or any other idea to prevent the outside spoofing?


you can certainly do

smtpd_recipient_restrictions =
    check_sender_access hash:/etc/postfix/access_sender

== access_sender:
mydomain.example REJECT blah blah
.mydomain.example REJECT blah blah