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Sourav
Asked: 2011-11-13 07:20:10 +0800 CST

How to restrict user from using different forged sender email in postfix?

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I am managing a mail server. The mail server is running with multiple domains configured. The problem is authenticated user can use any sender email ID and I need to prevent it. How can I do that?

Example: a sender with email [email protected] is sending mail with sender email address as [email protected]

I need to prevent that.

centos postfix

2 Answers

  1. You do this with the configuration option smtpd_sender_login_maps.

    It requires the user has SASL authenticated.

    smtpd_sender_login_maps (default: empty)

    Optional lookup table with the SASL login names that own sender
(MAIL FROM) addresses.

Specify zero or more "type:table" lookup tables. With lookups
from indexed files such as DB or DBM, or from networked tables 
such as NIS, LDAP or SQL, the following search operations
are done with a sender address of user@domain:

1) user@domain
    This table lookup is always done and has the highest precedence. 
2) user
    This table lookup is done only when the domain part of 
    the sender address matches $myorigin, $mydestination, 
    $inet_interfaces or $proxy_interfaces. 
3) @domain
    This table lookup is done last and has the lowest precedence. 

In all cases the result of table lookup must be either 
"not found" or a list of SASL login names separated by 
comma and/or whitespace.

    Then you add a configuration option along with the above to the smtpd_sender_restrictions optoin such as;

    smtpd_sender_restrictions = reject_authenticated_sender_login_mismatch
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  2. This works with Postfix 2.1+ If not, reject_sender_login_mismatch

    smtpd_sender_restrictions = reject_sender_login_mismatch

    According to postfix documentation
    reject_authenticated_sender_login_mismatch enforces reject_sender_login_mismatch

    reject_sender_login_mismatch: Reject the request when $smtpd_sender_login_maps specifies an owner for the MAIL FROM address, but the client is not (SASL) logged in as that MAIL FROM address owner; or when the client is (SASL) logged in, but the client login name doesn't own the MAIL FROM address according to $smtpd_sender_login_maps.

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