mail exploders

Andrew Tridgell tridge at
Wed Oct 28 09:29:27 GMT 1998

Thanks to everyone who offered to help out with mail exploding. Brian
Roberson was the first to offer so I went with his site. We are now
exploding mail for .edu, .com and .org via his site at

Some people indicated they didn't know how exploding works. The way it
works is that I configure listproc to put 20 recipients in each
message, with recipients sorted by reversed email address (so all the addresses are together). zmailer then has a config file like

.       smtpx!
.au     smtp!
.com    smtpx!
.edu    smtpx!
.nz     smtp!
.org    smtpx!

which says that all .au and .nz mail should be delivered directly, all
.com, .edu and .org mail should go via and all other
mail should go via

Those hosts then selectively enable SMTP relaying for They don't need to run any special software, they
just need to disable their relay rules for that one host.

The result is that only needs to deliver about 5% of
its full mail load, and even that goes very fast because it is all
done over a one connection. That saves us heaps of money as we pay a
lot for net access here in Australia.

I don't want to put in dozens of exploders because then the chance of
a failure goes way up. I would be happy to put in exploders for
particular regions if anyone offers, for example a european exploder
or a japanese exploder would make sense. Please don't offer unless you
have a reliable, maintained mail system, as when something goes wrong
it affects thousands of people and generates piles of hate mail.

Cheers, Tridge

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