Boucing mail to my smtp redirected domain

maxfloden · Post by **maxfloden** » Thu Mar 17, 2005 3:23 am

Someone trying to send email to my domain for which I use the rollernet smtp redirect service got this error message (I have replaced username and domain with xxx):

Hi. This is the qmail-send program at s3.loopia.se.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<xxx@xxx.com>:
67.118.43.92 does not like recipient.
Remote host said: 554 <xxx@xxx.com>: Recipient address rejected:
Blocked by bl.spamcop.net - Blocked - see
http://www.spamcop.net/bl.shtml?194.9.94.6
Giving up on 67.118.43.92.

--- Below this line is a copy of the message.

The error message seems strange to me, that rollernet/spamcop should say that the recipient is blocked? I thought it only blocked senders? (And as far as I know and hope I am not blocked by spamcop).
I have spamcop enabled as my bl filter on this domain in rollernet.

Is this a problem on his side or a problem with rollernet?

maxfloden · Post by **maxfloden** » Thu Mar 31, 2005 12:38 pm

Anyone that can help me decrypt this error message?
This same sender is still getting these every now and then, but most of the time it works fine for him sending email to me. Strange.

Post by **RollerNetSupport** » Thu Mar 31, 2005 1:19 pm

I don't think it's a problem with him or with us. The IP of whatever mail server he's coming from was rejected by SpamCop. I've noticed that SpamCop has very fast listing/delisting at times; an IP could end up in their blacklist for 15 minutes and then silently removed without any record why it was there. I usually use openrbl.org as a starting point to check IP addresses that are rejected due to some DNSBL. I did a search on 194.9.94.6 and it came up all clear, but that doesn't mean it wasn't listed in SpamCop's blacklist for a few minutes and then removed.

maxfloden · Post by **maxfloden** » Tue Apr 05, 2005 7:08 am

The thing that puzzles me is that it says "does not like recipient" and "Recipient address rejected". Shouldn't it say "sender"?

Post by **RollerNetSupport** » Tue Apr 05, 2005 9:07 am

Blocking takes place at the RCPT TO stage, so any rejects would be sent in response to each RCPT TO. This is the earliest point at which the filter has enough information to make DNSBL, SPF, and other filtering decisions. At the MAIL FROM stage, we have no idea who the message is destined for and how to apply filtering rules, so we can't filter yet. Bounce messages from other MTA's will vary, but here's what the raw SMTP session would look like:

Code: Select all

220 mail.rollernet.us ESMTP Postfix
EHLO rollernet.us
250-mail.rollernet.us
250-PIPELINING
250-SIZE 51200000
250-VRFY
250-ETRN
250 8BITMIME
MAIL FROM:<block@baddomain.com>
250 Ok
RCPT TO:<test@rollernet.us>
554 <test@rollernet.us>: Recipient address rejected: client blacklisted and can't send mail here!

The above example has "baddomain.com" in the blacklist filter for domain "rollernet.us".

It *could* say sender, but that's only possible if you apply filtering at a global level and reject after MAIL FROM. Since we handle a lot of mail for many domains, all with different filtering, we need to wait until we know where the mail is from and where it's going before any filtering (and rejections/deferments) can be done.