From: Alejandro Facultad (alejandro_facultadyahoo.com.ar)
Date: Thu Feb 07 2008 - 09:37:26 CST

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Magnus Bäck wrote:
> On Thursday, February 07, 2008 at 15:54 CET,
> Alejandro Facultad <alejandro_facultadyahoo.com.ar> wrote:
>
>> Dear all, I have Postfix 2.3.8 as my mail server and I want this: if
>> someone write a message to a non existant mail account from my domain,
>> he/she must get a response code = 250 and not 550. I want the same
>> response code that he/she will obtain in case of writting to an
>> existing mail account.
>
> What on earth would be the point of this? It will cause for problems
> for clients who think Postfix has accepted a recipient and continue
> with DATA, to which Postfix will respond that there aren't any valid
> recipients.
>
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> 220 mail.example.com ESMTP Postfix (2.3.2)
> HELO localhost
> 250 mail.example.com
> MAIL FROM:<>
> 250 2.1.0 Ok
> RCPT TO:<nonexistentuserexample.com>
> 250 2.1.5 Ok
> DATA
> 554 5.5.1 Error: no valid recipients

Here is the point, I want the same behaviour you say because we have
information that some people from Internet do just you write above and
when they get:

RCPT TO:<nonexistentuserexample.com>
250 2.1.5 Ok

this 250 indicates that the user from our organization is a valid user
and they get it, so they stop here and they don't follow with DATA
command.

We work for a government organization with sensible data, so our mails
can't be in public data bases.

If "intruder" do:

RCPT TO:<nonexistentuserexample.com>
250 2.1.5 Ok

they won't know wich mail account is valid or invalid, always get the
same code and this behaviour "ofuscate" the valid mail accounts.

Special thanks

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