Do some spammers ignore MX ptrs?

[BB]

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 medicine.wisc.edu> 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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