Re: 3rd party spam filter and virtual users

2 msg	Deliver mail using my ISP server
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2 msg	Address rewriting - converting an old domain to...
4 msg	Email routing like MX functionality

3rd party spam filter and virtual users
\ Lars Johansen (15 May 2007)
. \ Noel Jones (15 May 2007)
. \ John Evans (15 May 2007)
. . \ Victor Duchovni (15 May 2007)

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1 msg	tlsmgr on solaris9
6 msg	sasl problem

Subject:	Re: 3rd party spam filter and virtual users
Group:	Postfix-users
From:	Victor Duchovni
Date:	15 May 2007

On Tue, May 15, 2007 at 11:30:01AM -0600, John Evans wrote:

> On Tue, 15 May 2007, Lars Johansen wrote:
>
> >Hi we have a setup with postfixadmin and virtual users.. everything
> >works great, but we have one issue.
> >
> >We want to use a 3rd party spam service provider.. but we dont want to
> >set our MX records to them..
> >
>
> I work for one of those "third party spam service providers" (no, I can't
> which one, sorry.)
>
> If you receive all of your email, forward it to a 3rd party, ask them to
> filter it, and send legitimate mail back to you, you're going to be
> blowing a huge amount of bandwidth. You'll be sending spam messages
> through your pipe at least twice, and legitimate mail through at least
> three times. Not a good idea.

Only if bandwidth is noticeably expensive, email is not a large fraction
of overall bandwidth for large organizations, ...

> Also, most third part spam service providers use some form of IP
> reputation schema. This means that you will be sending all of your mail
> flow (including spam) to them, and this will poison their IP reputation
> database AGAINST you.

Only if implemented poorly (say without XFORWARD or topmost received
header parsing), don't use 3rd parties that do the job poorly.

--
Viktor.

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