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Date:	Thu, 6 May 2004 11:12:20 PDT7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Mail Server: varying list delays

Content Type: text/plain

On SCOUG-Help this morning is a two-message thread titled "list delays
gone". It concerns delays in receiving messages sent to SCOUG-Help.

You may wish to help Bob with his Communigate testing and develop a test
he can use to determine how Communigate acts under either of the
following conditions:

-- No response from list member's SMTP server. There seem to be three
list addresses which occasionally cause problems -- @peterskye.com
(hosted by ZoneEdit), @pacbell.net and @well.com. When one or more of
these isn't responding, InetMail "sits and waits" before timing out and
requeueing the message, and this can really slow things down if there
are a lot of messages backed up for these targets. Early this morning
there were perhaps 100 messages in the queue that were waiting for
delivery, and all but one of them were spam. I don't see any indication
that InetMail attempts to send out messages in parallel with multiple
threads; the design seems to be there but for some reason only one
message at a time is "locked". Paralleling all these message sends
might also saturate Sundial's line so we don't want to just remove some
limit on parallel threads.

-- Invalid "From:" address on message sent to list server. The list
server (Steward under InetMail) receives two types of these messages:
1) spam messages from senders who aren't list members and attempts are
made to return these messages, and 2) spam messages to the list agent
address where you normally make "subscribe me" requests but attempts to
return these messages are made because their content is not understood.

-- Some kind of cap on incoming messages per connection. Some of the
spammers send dozens of messages per connection; some even make multiple
connections (i.e. more than one SMTP socket with the same foreign IP
address). I've logged the IP addresses of the spammers (netstat on a
five-minute loop) for weeks and there's no pattern so I can't block
certain IP addresses at the router. A five-minute loop is too long for
full IP capture but it has shown that the spammers are using lots of
different SMTP servers. Sometimes the spammers connect directly to the
SCOUG server, and sometimes their messages come through ZoneEdit which
hosts the scoug.com MX domain.

- Peter

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