Monthly Archives: July 2011

DNS: Sends No Mail

I really wish there was a way to indicate, in DNS, that a domain never sends mail.

That way, if a mail server recieves mail claiming to be from that domain, it can be discarded out of hand.

I’ve got a bunch of domains that JUST do web serving … they never send mail.  If the web server that they are hosted on does send mail, it’s sent from via the mail server (and is identified as such).

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I think most developers I know (and I know quite a few) will identify with this blog post.

Have you ever wondered why something on your computer will work fine while you’re working on it (or developing it) but, suddenly and without warning, fail to work properly when you’re showing someone what you are working on?

This often happens when someone asks you if there’s a way to accomplish something … and you say: “Sure, that’s easy”, and try to show them … failing miserably.

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DKIM Rule – SpamAssassin

I put together a new SpamAssassin rule that will help identify spam from spoofed email addresses.

Some email providers always sign email with DKIM or DomainKeys … based on this assumption, if you get a message from one of those domains and it isn’t signed, you can assume its more likely to be spam.

This particular rule operates on the assumption that all mail from Yahoo & Gmail will be signed.  It does not, however, raise the score a huge amount … because it’s just more LIKELY to be spam if it’s not signed … it’s not guaranteed to be spam. Some people may use the Yahoo or Gmail account’s in the from address, but not actually send from that service.
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Xen, LVM, and Grub

I ran into an interesting problem with my new server the other day.

Due to a hardware problem with an external USB hard drive, I had to reboot the XEN host.

I had to do the reboot remotely … so I couldn’t intervene if something went wrong.  Yes, you guessed it, something did go wrong.

When I finally got home I found the system trying to boot ‘bree’ … which is one of the XEN guest machines.

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