Do some spammers ignore MX ptrs?

[Jethro R Binks]

On Thu, 27 Apr 2006, Michael Masse 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?

Both.

Don't run an SMTP listener on the machine bound to that IP address if you 
don't want it to receive mail, or limit who can talk to it by means of 
firewalls/MTA restrictions/etc.

Jethro.

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Jethro R Binks
Computing Officer, IT Services
University Of Strathclyde, Glasgow, UK