Martin Read <zen75...@zen.co.uk> writes: > On 12/10/14 15:53, lee wrote: >> And when they are filtered, does the sender get a message telling him >> that their message hasn't been delivered? > > The requirement in RFC 2821 (the successor to RFC 821 which you've > recently been referring to) section 4.2.5 that a server which issues a > 2yz completion status after final dot must return appropriate > notification to the sender cannot be fulfilled is an unreasonable > demand in the modern era. > > If you wait for all filtering to complete before issuing a response to > final dot, your mail server is vulnerable to denial-of-service attacks > unless you undercook your filtering; if you issue a 2yz status before > filtering is complete, then send the notifications demanded by RFC > 2821 if the deferred filtering results in a rejection, your mail > server is now a public nuisance because of the amount of backscatter > it generates.
All this is no reason to violate RFCs. Besides, the idea is to avoid content filtering and to reject a message instead of accepting it. -- Again we must be afraid of speaking of daemons for fear that daemons might swallow us. Finally, this fear has become reasonable. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/871tqdxmmh....@yun.yagibdah.de
