[CentOS] Re: Postfix / Postini question

Wed Jun 29 15:26:25 UTC 2005
Ugo Bellavance <ugob at camo-route.com>

Marc Powell wrote:
> 
>>-----Original Message-----
>>From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On
>>Behalf Of Barry Brimer
>>Sent: Wednesday, June 29, 2005 9:47 AM
>>To: centos at centos.org
>>Subject: [CentOS] Postfix / Postini question
>>
>>
>>
>>I have a mail server that handles several domains.  One of these
> 
> domains
> 
>>has
>>decided to use Postini.  For those not familiar with Postini, you set
> 
> your
> 
>>MX
>>records to use their mail servers.  They filter mail, and deliver you
> 
> only
> 
>>the
>>clean virus/spam free mail.  The idea is to only allow incoming mail
> 
> from
> 
>>their
>>mail servers so spammers are unable to send to your mail server
> 
> directly.
> 
>>This
>>is fairly simple to do with standard restriction classes for a
> 
> dedicated
> 
>>mail
>>server.  I am not sure how to accomplish this on a shared mail server.
>>Ideally
>>I would like to instruct postfix to accept mail from anywhere for all
>>domains
>>except one domain (the one using Postini) and only allow mail destined
> 
> for
> 
>>that
>>specific domain to originate from Postini's mail servers.  Any ideas
> 
> would
> 
>>be
>>greatly appreciated.
> 
> 
> 
> I'm not a postfix guru but I don't believe that is possible with a
> shared server. However, it's been my experience that if your server is
> not listed as an MX (and it won't), MXs exist (and they will --
> Postini's) then mail will not be delivered to your machine by anyone
> except Postini. The only two scenarios I am aware of in which mail would
> get delivered to your server instead of Postini's would be if a) you
> were listed as a fallback MX or b) no MX's were specified then the A
> record for your domain would be used.

That is not quite true.  Spammers will try the A records to send spam.
Not that much, but they will.

> 
> Have you looked through the postfix wiki, documentation, faq, mailing
> list, etc? That'd be the first place I'd go since they _are_ the postfix
> experts ;).
> 
> --
> Marc