DCC - Postfix MTA mail hub implementation question

Paul Vixie paul@vix.com
Fri Aug 23 20:11:26 UTC 2002

> That's the crux -- is there any DCC or general filtering protocol useful 
> enough to be adopted by multiple MTAs? Or, will DCC have to conform to 
> each MTA's filtering protocol as it has for sendmail? I think the latter 
> is more likely.

the milter API is actually very general and it's possible that postfix
could just adopt it.

> One benchmark to look at may be virus checkers. Many of them offer to 
> act as pseudo SMTP servers -- either in front of the real MTA or behind 
> it in a filtering step in the SMTP chain. This is an example of a class 
> of application with needs similar to DCC that has failed to foster a 
> universal content filtering protocol (beyond SMTP itself).

if you're rejecting e-mail at the MTA level because it is invalid or
unwanted, then such rejection must be done synchronously (before the
final 250) or else you're stuck with unbouncable garbage and you've put
no disincentive on the sender to puke more of it in your direction.

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