[Mailman-Developers] before next release: disable backscatter in default installation

[Barry Warsaw]

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On Mar 26, 2008, at 7:27 AM, Ian Eiloart wrote:
>
>>
>> I think you will be happier with what is possible in Mailman 3.  In
>> mm3 we have a working LMTP server, those it's based on asyncore and
>> its scalability is questionable.  Although I have not yet done  
>> this, I
>> plan to tie the rule chain checker into LMTP so that if your MTA
>> supports LMTP delivery the following can happen:
>>
>> worldwildwonderland -> SMTP -> MM's LMTP -> rule checks
>>
>> The rule checks then could tell LTMP to reject the message right
>> there, which would return 5xx to SMTP and /it/ would return 5xx to
>> whatever upstream SMTP its talking to.
>>
>> Now, I wouldn't want to do a lot of work at that point, but some
>> simple checks would definitely be possible.  You can reject messages
>> as early in the process as possible and do it at the SMTP layer.
>
> It needs to be done after RCPT TO.  LMTP allows you to sensibly do  
> this
> later, and get return codes for individual recipients. However, it  
> we're
> doing this with call forwards from an MTA which is receiving email  
> over
> SMTP, then the MTA will have to check the sender/recipient pair at  
> RCPT TO
> time.
>
> on connect:
> accept the connection
> HELO/EHLO:
> reject if the sending MTA isn't known
> MAIL FROM:
> accept (perhaps unless the sender address is forbidden to post to all
> lists).
> RCPT TO:
> accept if the sender has permissions to post to the list, otherwise  
> reject.
> This is the last chance to give a list specific response to an MTA  
> that is
> engaged in a callout.
> DATA:
> reject null senders here if appropriate. Rejecting a null sender at  
> RCPT TO
> or earlier might break callouts.
> .............
> .
> Check the data, reject if inappropriate for a specific list (but  
> this is
> likely to cause a bounce from our MTA). Because we've decided to  
> trust the
> sender, we should be OK to bounce a message here, unless the list is  
> an
> open list.

This is great.  I've captured it on the wiki: http://wiki.list.org/display/DEV/LMTP+process

- -Barry

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