[nzlug] Understanding email DNS

[Robin Sheat]

On Thursday 05 October 2006 23:53, Warren Boyd wrote:
> However, one thing to note with your backups is that they *will*  
> experience traffic even when your primaries are all operational.
Oh, yes, I see that a bit.

> This comes from many "spam engines" having brain dead DNS resolution  
> routines and just using whatever comes up first as the point it's  
> going to use.  
Also, the theory goes, that there may be less virus/spam scanning on the 
secondaries.

> I've seen a few comments about marking spammers as all   
> those that hit the secondaries ...
Bad idea. If there's a transient network failure between you and the sender, 
they should try the backup, and they may get through. That's a completely 
legitimate use of backup servers.

> I think I recall seeing that in the event of no MX record, mail  
> servers should attempt to use the A record.  Someone more up to speed  
> with the RFC's might be able to point out if this is legitimate?
I'm pretty sure you're correct there. I think I used to do it that way, and it 
worked fine.

-- 
Robin <robin at kallisti.net.nz> JabberID: <eythian at jabber.kallisti.net.nz>

Hostes alienigeni me abduxerunt. Qui annus est?

PGP Key 0xA99CEB6D = 5957 6D23 8B16 EFAB FEF8  7175 14D3 6485 A99C EB6D
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 191 bytes
Desc: not available
Url : http://www.linux.net.nz/pipermail/nzlug/attachments/20061006/0f2ca295/attachment.pgp