On 10/05/2014 05:40 AM, Henrik Larsson wrote: > I'm sure not able to give you any evidence that this would lower the > amount of spam. But giving a spammer, or a malicious user a clue about > why the mail was blocked, could make him try to find ways around it. > > Even if it is just about my warm fuzzy feelings, it's just about giving > the administrator a choice if you want to reveal this information or > not. If I had the choice I would remove this information from the > output. Just like I have configured "show_user_unknown_table_name" not > to reveal information about my mailbox tables.
You make an assumption that, based on the software that spammers use, is false to fact: that they record the rejection reasons. My own analysis of some of the spam-sending software is that they don't have any significant form of logging. The software doesn't care. And, frankly, neither does the spammer. Especially the stealth spammers. The problem for some spammers is that their spam is sent using "fire and forget" methods, such as injection via bad CGI on Web sites. They never see the results of their transmissions, other than to see the response rate drop. Relay abusers never see the results, either, because they use false source addresses so the bounce messages from the relay never get back to the spammer. That said, if you don't want to expose the reason for the rejection, PostFix gives you that ability, although not necessarily the way that you want it. The way to do that is to write a policy filter that will detect the problems, and return status to PostFix to say "reject this mail for policy reasons" without being specific. If this is important to you, you will go to the effort. The policy filter isn't hard to write; I did the initial version in Perl in a couple of hours. As I gained more experience, I put in additional features. The reason I did the extra work was that my customers had varying requirements for mail delivery, so the policy filter customized the checking/blocking for each domain, and in some instances by specific mail addresses.
