Do some spammers ignore MX ptrs?

Chris Sweeney csweeney at
Thu Apr 27 15:22:15 IST 2006

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Why have a secondary of you are going to just blacklist everything
from it?  Why not save the power and just have one MX then?

BB wrote:
> I think some do.  I have a secondary MX record for a domain hosted
> by my ISP.  Legitimate traffic really should never be delivered to
> this server when the primary waited zero server is up.
> Looks to me all mail coming from this secondary is spam.  Think the
> spammers hope the backup relay does not filter for spam, which
> appears to be true.  And then the primary accepts all from the
> secondary.
> I blacklist all mail from this secondary.
> Been doing this for three years without any problems.
> Your issue might also be related to DNS.
> On 4/27/06, * Michael Masse* <mrm at
> <mailto:mrm at>> wrote:
>     I'm offloading just Mailscanner services from an overloaded
>     email store
>     machine to a new machine and am doing so by pointing the MX
>     record for
>     the domain to the new machine.   The A ptr still points to the old
>     system so that none of the other services this machine provides get
>     interupted.     All legitimate email and most spam is going to
>     the new
>     system like it's supposed to and it then gets relayed to the old
>     store
>     machine, but I'm noticing quite a bit of spam is still being sent
>     directly to the old system.     Does some spam software ignore
>     the MX
>     ptr and go to the A ptr instead, or is this more likely to be a DNS
>     cache issue on the sending systems that will hopefully clear
>     itself out
>     over a few days?
>     Mike
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- --
Thanks Chris

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csweeney at
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