Latency on Beowulf Mailing list

Donald Becker becker at
Fri Dec 5 15:28:42 EST 2003

On Fri, 5 Dec 2003, Erwan Velu wrote:

> When I'm sending messages to beowulf mailing list, I can see them after
> 8 hours :(
> Sometimes, my answers are too old for being intresting :(
> Any ideas? Does other users are in the same case ?

The quick answer is "spammers and viruses".

There are several reasons that this is the case:
  Over 95% of Beowulf list postings are held for moderation
  The Beowulf list alone has about 3000 addresses

95% might seem large, but considering only 1 in ten attempted postings
is valid, only about 50% of the posts are held for moderation.  While I
do sometimes wake up in the middle of the night to moderate, you
shouldn't really expect that.

A posting may be held for moderation by match any of about 25 patterns.
Some of those patterns are pretty general -- even certain three digit
numbers and two digit country codes will trigger moderation.

Once held for moderation the posting may be automatically deleted.
Right now there are 1439 phrases and 3298 IP address prefixes and domain
names.  All were hand added.  My goal is over 90% automatic deletions.
If I stop adding rules, it drops below that number in a week or two as
spammers move machines and change tactics.

Less common is that a post is automatically approved.  Some spammers
have taken to including sections of web pages in their email, so don't
expect this increasing in the future.

The second point is also a result of spammers, albeit indirectly.  The
list is run by mailman, which splits the list up into sections.  If your
position is after a Teergruber, or the link is just busy, your email
will be delayed for several hours.  Despite being very responsible
mailers, our machine (or perhaps our IP address block) does sometimes
end up on a RBL.

I see this problem as only getting worse.  Our "3c509" mailing list is
first alphabetically, and thus is the first recipient of new spam.  I've
mostly given up on it, but leave it in place to harvest new patterns.
It received 5 new messages in the past 30 minutes, a rate up
substantially over just a few months ago. 

So, what can you do to avoid delays?  Nothing especially predictable,
because predictable measures are easily defeated by spammers.  But you
- avoid posting or having a return address from free mail account services
- have a reverse-resolving host name on all mail hops
- don't have "adsl" or "dialup" in the header
- avoid all mention of "personal enhancement" drugs, purchasing drugs of
    any kind, moving money out of your sub-sahara country, mentions of
    credit card names, sex with a farm animal, sex with multiple farm
    animals, webcams, etc.  Talking about your cluster of webcams of
    viagra-enhanced farm animals trying to move their lottery winnings
    out of from Nigeria, even if they puchased the viagra at dicount
    rates from Canadian suppliers that included a free mini-rc car could
    conceivably be brought on-topic, but that posting will never make it.

Donald Becker				becker at
Scyld Computing Corporation
914 Bay Ridge Road, Suite 220		Scyld Beowulf cluster systems
Annapolis MD 21403			410-990-9993

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