How about this? Have 2 mail servers. The backup kept in sync w/ the primary using rsync or something along that line. Only the primary is in the dns. Have a script on your dns ping the primary mail server and if it gets a response do nothing. If it doesn't get a response the script then edits the db files on the dns server, changes the serial number in the files and restarts named. The backup is now the primary. Or to be a little more sophisticated you could have the script query the primary mail server with an expect script using esmtp. This makes sure that esmtp is responding not just that the primary mail server is still on the network. You need to be running your own dns and mail servers to do this. I haven't had the time to do this myself but I know that my boss would go ballistic if he didn't have email for more than a couple hours. Of course he doesn't want to pay for HA. It was all I could do to get a Dell 1750 with raid 5 and dual power supplies to build my mail server on. Email is his lifeline and he considers it critical.On Mon, May 16, 2005 at 08:59:32PM +0100, James Wilkinson wrote:
And this is the problem: by the time any MX has accepted e-mail for you, you've lost the chance to do a whole set of anti-spam checks. If you control the backup MX, you can set it to do the same checks as your main MX. If you don't, then your backup MX is a highway around your anti-spam defences. And spammers know this. Their tools know this.
This just amounts to "don't use an ummaintained machine with no anti-spam tools for your backup MX". I don't see why that in any way invalidates the whole idea. (In fact, for the reasons you describe, one might want to have *stricter* spam checking rules on the backup MX.)
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