Do some spammers ignore MX ptrs?

cobalt-users1 at cobalt-users1 at
Thu Apr 27 15:41:17 IST 2006

On 27 Apr 2006 at 8:30, 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?   


Its not just spammers but bad programmers as well.  Several years ago I noticed that behaviour 
in some Windows email systems.  It may have been fixed now.

I never put an A record in for domain unless there is a very good reason.

Ian Gibbons                                                  
Fish.Net Ltd                     Providing Internet Solutions      e-mail IanGibbons at
Tel +44 (0)1457 819600                 Fax +44 (0)1457 819602         

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