Charles Mills wrote:
I sent this once already but it seems to have disappeared entirely --
neither posted nor bounced.
I halfway "get" DNS and SMTP and all that but I am not sufficiently an
expert to debate with someone who thinks they are. Here is the server log
supplied by my ISP for one of the bounces:
Feb 20 10:52:42 mailfe qmail: 1455994362.370707 delivery 826049: deferral:
Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)/_130.160.0.24
:_Timeout_connecting/
Okay, once they are having problems with you, they put you on a timeout, e.g.,
60 seconds between the last
transaction and the next connection of the suspicious server (your server)
They're using a free, low-volume service uribl.com to do reverse DNS lookups on SMTP clients such as your server that
contact UA.
Reverse DNS tries to establish that your server *might conceivably* be who it says it is. Passing a Reverse DNS query
doesn't mean you're not a spammer,
but failing such a query proves you are. uribl.com exists to facilitate such
queries for low-volume servers.
If UA uses uribl.com too often in a minute, uribl.com which is a low-volume, free service sends back a failure message
triggering a SpamAssassin rule:
"X-Gwh-Spam-Flags:
BAYES_00,FROM_LOCAL_HEX,FROM_STARTS_WITH_NUMS,RCVD_IN_DNSWL_LOW,URIBL_BLOCKED"
The rule is URLBL_BLOCKED .. UA then decides to reject your message.
I'm assuming it's the "too often" problem There are other problems, e.g., intermittent misconfiguration of the request
to uribl.com that could cause uribl.com to refuse the request.
--
Jack J. Woehr # Science is more than a body of knowledge. It's a way of
www.well.com/~jax # thinking, a way of skeptically interrogating the universe
www.softwoehr.com # with a fine understanding of human fallibility. - Carl Sagan
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