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13 messages in net.sourceforge.lists.courier-usersRe: [courier-users] Considerable time...| From | Sent On | Attachments |
|---|---|---|
| Sándor Zsolt | May 26, 2006 2:25 am | |
| Daniel Faber | May 26, 2006 3:32 am | |
| Sam Varshavchik | May 26, 2006 3:50 am | |
| Sándor Zsolt | May 26, 2006 5:36 am | |
| Gordon Messmer | May 26, 2006 9:52 am | |
| Daniel Faber | May 26, 2006 10:33 am | |
| Gordon Messmer | May 26, 2006 10:40 am | |
| Arno | May 26, 2006 11:26 am | |
| Daniel Faber | May 26, 2006 12:10 pm | |
| Sándor Zsolt | May 29, 2006 2:51 am | |
| Sam Varshavchik | May 29, 2006 6:16 am | |
| Sándor Zsolt | May 30, 2006 12:26 am | |
| Sam Varshavchik | May 30, 2006 3:55 am |
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| Subject: | Re: [courier-users] Considerable time when "550 unknown user" error msg. at local domain | Actions... |
|---|---|---|
| From: | Arno (ar...@disconnect.de) | |
| Date: | May 26, 2006 11:26:38 am | |
| List: | net.sourceforge.lists.courier-users | |
Hi Sándor,
On Friday 26 May 2006 19:40, Gordon Messmer wrote:
As practical advice, I recommend against doing so. By doing so, you're solving the wrong problem. If your mail filter is accepting mail without validating the recipients, and passing it on to courier, you can bet that you're going to generate a *ton* of backscatter. Now, first, the problem is going to be that you're going to bounce a whole lot of mail to people who didn't sent it, but whose address was hijacked by spammers. Eventually, the problem is going to hit you, too. The mail queue on the firewall is going to fill with tens of thousands of messages that can't be delivered, because the recipient address is invalid, and can't be bounced, because the source address is invalid, too. Once that happens, valid deliveries are going to start taking a very long time, again.
Really, you want your "firewall" to validate recipient addresses.
If you need a second opinion on this: I can only stronlgy second Gordon's advice. About 1 year my primary MX for ~300 domains ran qmail without any patches. QMail in its standard distribution is not capable of rejecting mails on SMTP-Level. It first accepts any mail, and then checks if the email-address is valid, and if not, a Non-Delivery-Notification is generated.
I was swamped with backscatter and the server was more busy trying to deliver the Non-Delivery-Notifications than delivering legit mails. There were almost always 1000+ mails in my queue, most of them backscatter.
Then I switched to courier with mail rejection on SMTP-Level. To give you some figures: the average number of mails in the queue is now ~50. And if you're paying for your traffic by volume you be interested in the fact that I was able to cut my mail-traffic down to 1/10th after I switched to courier. With QMail I had about 300GB per month, with courier I have a mere 30GB per month.
The bottom line being: maybe you should consider setting up a courier server who knows all valid e-mail-addresses in a DMZ and then forwards any _valid_ e-mail through via the firewall to a courier server behind the firewall. Otherwise you could try to turn off the SMTP-proxy in your firewall and do a straight port forwarding letting the courier server behind your firewall handle all the SMTP-traffic (though for security reasons I'd strongly suggest setting up the DMZ).
HTH and I didn't bore you :)
-- Regards,
Arno.