Girish Kulkarni skrev:
You got a link with a good technical explanation in another reply. The importance of that info may not be apparent if you are not familiar with how email works. Let me try an analogy. Imagine email is just like regular mail exept that everything is delivered by the sender in person to a local post-office, which runs a truck with the mail to the recipient's local post-office. All recipients pick up their mail at their local post-office. A mail-server is a post-office. Every time mail enters a post-office, it puts a "Received" line on the envelope, latest at the top.On Wed, 30 Sep 2009, Ric Otte wrote:I believe it is bad to use procmail to reject mail, ...Why is that?
Say you go pick up all your mail and bring it home to sort at the kitchen-table. The kitchen-table is procmail. You find junk-mail in the pile on your kitchen-table and label it "return to sender" and bring it back to the post-office. On the internet all junk-mail in practice has forged sender address, so some innocent soul will get his mail-box filled with "returns" that are actually not from him. The better way to deal with junk-mail is to have your local post-office simply refuse any mail from dubious commercial mass-mailers. That way innocent by-standers are protected, and resources taken by bringing the junk all the way to your kitchen-table are saved. If the mail was in fact not junk, the real sender will be notified by his own local post-office of the failure, because local post-offices will usually notify local customers when their truck was unable to deliver. The recipient's post-office can in some cases even inspect the contens of the mail WHILE THE DELIVERY VAN IS WAITING and say "No thanks". This is the stage of delivery postfix calls "Before-queue", and you want to reject as much as possible at this stage, before the mail is put into your P.O.Box. Postfix can also mark mail to be filtered, in effect have a clerk go over the mail that is to be put into your P.O.Box after the delivery truck has left. At this stage postfix can bounce stuff back to the sender (REJECT action), but usually it is not advisable to do so. Just let postfix "drop it on the floor" (DISCARD action). I imagine exim has similar options.
P.S: One effective way to send out loads of spam, is to send it to non-existant adresses hosted on innocent, but misconfigured, mail-servers. This misguided, old-fashioned post-office will then proceed to deliver the entire mail "back" to the "sender" in its own misguided mind, while it actually is helping spread spam by using its good name and delivery system to deliver the spam mail to a third party. In this day and age incompetence is actually just another name for evil, and such old-timers will be summarliy put into a lot of RBL-lists.