Re: [exim] Spoofed email address in From: header

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Lähettäjä: Heiko Schlittermann
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Vastaanottaja: exim-users
Aihe: Re: [exim] Spoofed email address in From: header
web@??? <web@???> (Mi 08 Mai 2013 11:37:01 CEST):
> Hi
>
> I've found that after checking header_syntax for incoming email, I
> have false positive rejections in email that have:
>
> <Undisclosed-Recipient:;>
>
> set as "To:" header , sample error:
>
>
> 2013-05-08 11:25:55 1Ua0dH-00055F-4O H=v095439.home.net.pl
> [79.96.175.189] F=<al@???> rejected after DATA: "@" or "."
> expected after "Undisclosed-Recipient": failing address in "To:"
> header is: <Undisclosed-Recipient:;>
>
> 2013-05-08 11:27:31 1Ua0eo-0006JM-QZ H=ans229.rev.netart.pl
> [85.128.227.229] F=<sekretariat@???> rejected after DATA:
> "@" or "." expected after "Undisclosed-Recipient": failing address
> in "To:" header is: <Undisclosed-Recipient:;>
>
> Do you have any solution for this?


    https://github.com/Exim/exim/wiki/AclSmtpData


But my solution is to reject such messages, and neither me nor our
customers seem to miss anything. If the client is not able to produce a
RFC conformant group address, I do not like it's messages.


    OK: To: Undisclosed Recipients:;
   !OK: To: <Undisclosed Recipients:;>


Just verfied with the micro sample config:
~~~[/tmp/x]
acl_smtp_rcpt = accept
acl_smtp_data = accept verify = header_syntax
~~~

sudo swaks --header 'To: Undisclosed Recipients:;' --pipe 'exim -bh 8.8.8.8 -C /tmp/x' -f luser@??? -t luser@???
vs.
sudo swaks --header 'To: <Undisclosed Recipients:;>' --pipe 'exim -bh 8.8.8.8 -C /tmp/x' -f luser@??? -t luser@???

I checked my reject logs. Mostly the senders look like known or unknown
spammers. If the header is technically correct (w/o the < and >) the
messages go through.

Maybe you should check it using a legitimate MUA and send a message only
via BCC.


    Best regards from Dresden/Germany
    Viele Grüße aus Dresden
    Heiko Schlittermann
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