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31 Mar 2012

IPv6 DNS blacklists reconsidered Email

I opined about a year ago that DNS blacklists wouldn't work for mail that runs over IPv6 rather than IPv4. The reason is that IPv6 has such a huge range of addresses that spammers can easily send every message from a unique IP address, which means that recipient systems will fire off a unique set of DNSBL queries for every message, which will swamp DNS caches, since they won't be able to reuse cached results from previous queries like they can for IPv4 mail.

Now I'm much less sure this will be a problem, because it's not clear that DNSBL results benefit from caches now.

See more ...


posted at: 16:01 :: permanent link to this entry :: 2 comments
Trackback link is http://jl.ly/Email/v6blre.trackback

05 Mar 2012

Forwarding mail for your users Email

Courtesy forwards have been a standard feature of e-mail systems about as long as there have been e-mail systems. A user moves or changes jobs or something, and rather than just closing the account, the mail system forwards all the mail to the user's new address. Or a user with multiple addresses forwards them all to one place to be able to read all the mail together. Since forwarding is very cheap, it's quite common for forwards to persist for many years.

Unfortunately, forwarding is yet another thing that spam has screwed up. If you just forward all the mail that arrives at a typical address, most of what you'll be forwarding is spam. From the point of view of the system you're forwarding to, you're the one sending the spam, and they're likely to block you.

Fortuately, there are some ways to mitigate the damage.

See more ...


posted at: 21:06 :: permanent link to this entry :: 0 comments
Trackback link is http://jl.ly/Email/forward.trackback

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