Tomasz wrote: > Michael Katz schrieb: >> Tomasz Chmielewski wrote: >>> Martin J. Boeck schrieb: >>>> Hi! >>>> >>>> I was thinking about this some time ago. The problem would be, that >>>> you have to accept the message to scan it for a spam level with >>>> amavis. So you cannot reject it anymore. >>> >>> No, you're wrong - just do before-queue filtering. For example, for >>> Postfix, you'll find instructions here (Postfix Before-Queue Content >>> Filter): >>> >>> http://www.postfix.org/SMTPD_PROXY_README.html >> >> Pre-queue content filtering is the worst of all worlds
> I kindly disagree. >> - you lose the >> benefit of pre-queue filtering by accepting smtp data > What do you mean by a) "pre-queue filtering" and b) "pre-queue content > filtering"? > You mean by a) only the SMTP commands sent (IP, sender, recipient, RBLs > etc.). > But b), or "pre-queue content filtering", doesn't exclude it. >> while losing the >> benefit of postfix smtp scalability since you are putting a resource hog >> in the smtp process. > Is this claim valid? In both cases, you have exactly the same amount of > mails to filter. In "pre-queue content filtering" you need to have > enough resources to do the filtering during the connection, it's all a > function of the amount of emails and the processing power of the > filtering server... On a powerful lightly loaded server it can work. On a heavily loaded server it's not practical. Using an after-queue filter allows Postfix to buffer messages. Picture the difference. It's the busiest shopping day of the year before Christmas and there are only 2 cashiers at a major retailer. A before-queue filter makes everyone wait outside in the cold until the next cashier is available. Some will get tired of this crap and leave. They may come back later or eventually they may not. If both cashiers have problems with their registers no one gets in the door at all. With an after-queue filter everyone is allowed in the store. They may have to wait an hour before they reach the cashier, but at least we have their business. At some point the number of customers coming in the front door may subside. This allows the cashiers to get caught up. >> You do gain the marginal benefit of being able to >> reject spam that content filters find and smtp level tests do not >> identify, but many sites quarantine or discard or mark spam rather than >> rejecting, so this is only a benefit for some sites. > I wouldn't call it a "marginal benefit" - it's really important. It would be nice but because of the lengthy delay imposed by the content filter it only works well when the cashiers can keep up with the customers. > It also means your mail server doesn't have to deal with delivering of > bounces/reject messages that have false senders; also, your server > doesn't send those bounces/reject messages to all innocent people who > just happened to be in some spambot's FROM: field (rejected spam mails, > rejected mails with viruses etc.), so ironically, it also saves some > resources. Gary V ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ AMaViS-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/amavis-user AMaViS-FAQ:http://www.amavis.org/amavis-faq.php3 AMaViS-HowTos:http://www.amavis.org/howto/
