DJB's Internet Mail 2000 [LWN.net]

DJB's Internet Mail 2000

Posted Dec 19, 2003 0:25 UTC (Fri) by Ross (subscriber, #4065)
In reply to: DJB's Internet Mail 2000 by jhohm
Parent article: Spam-proofing the mail system

There would be a few problems with that. For one, what keeps people from
changing messages after you read them, or even deleting them before you
read them? What happens when their site is down? What happens when
that ISP goes out of business? That's a different type of communication
that what we know of as email. Making local copies on your ISP's mail
server would eleminate many of those problems but that kind of defeats
the purpose.

And worst of all spammers would still be a nuisance... they would not take
up storage for the entire spam, only the spam headers. Ok, that seems
like an improvement. But the bigger problem with spam is the distraction
and annoyance to the users when they checking their email. Now if they
want to do filtering they are required to connect to the spammer's server
to view the content. This lets the spammer know what addresses are alive
and being used. Any automated filtering will be slowed to a crawl due to
all the outgoing connections. I can even imagine situations where spammers
could use forged headers to cause mail servers to perform denial of service
attacks against third parties. And finally there would be an annoying
amount of latency between selecting a messages and reading the contents.

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DJB's Internet Mail 2000

Posted Dec 25, 2003 21:45 UTC (Thu) by jbayko (guest, #3493) [Link]

There would be a few problems with that. For one, what keeps people from changing messages after you read them

You could save them locally, as now (when messages are stored on an ISP email server, vs. stored on the sending server).

or even deleting them before you read them?

I think it's fair for the sender to change their mind. Your email client would simply compare the tag with what's on the server, notice the message is gone, and not even show it to you (unless you have it configured to show you deleted messages)

What happens when their site is down?

I'm sure you could configure your software to retry over a period of time, or a number of attempts - the same as when you send email, and the receiving server is down.

What happens when that ISP goes out of business?

What happens when your ISP goes out of business before you download your email? As with that case, the sender has the option of re-sending (and they're more likely to know things went wrong on their end than on your end).

That's a different type of communication that what we know of as email. Making local copies on your ISP's mail server would eleminate many of those problems but that kind of defeats the purpose.

Not really - the purpose is to make the sender incur a reasonable, but unavoidable and deterring cost.

[...] But the bigger problem with spam is the distraction and annoyance to the users when they checking their email. Now if they want to do filtering they are required to connect to the spammer's server to view the content.

Not necessarily:

It is much easier to blacklist the sender, since the source can be unambiguously identified. Checking a blacklist server will mean messages do not need to be loaded at all.
If the sender is shut down by their ISP, the message disappears and the recipient never needs to know it even existed.

This lets the spammer know what addresses are alive and being used.

And vice-versa.

Any automated filtering will be slowed to a crawl due to all the outgoing connections.

This could be a problem. But email is typically text, and takes less bandwidth than the images that are part of web pages, and web traffic isn't too bad.

I can even imagine situations where spammers could use forged headers to cause mail servers to perform denial of service attacks against third parties.

This could be a problem, if headers were not encrypted using some sort of strong public key.

And finally there would be an annoying amount of latency between selecting a messages and reading the contents.

Not any more than messages stored on an ISP - they (valid messages) can be downloaded while you're looking at the subject lines.