Virtual Alias Routing

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Virtual Alias Routing

James MacLachlan
Hi List,

I have read the documentation, and do not understand if this is possible,
but I think it should be.  I have a spam filter that is required to listen
on the MX of my domain, but it does not support alias expansion, so the
postfix server has to do the expansion then send the message back to the
filter for final delivery.

Is it possible to deliver virtual mailbox maps to the mda, but relay
virtual alias maps back to the filter?

I was thinking that I could append a routing domain to all aliases, which
would transport to a rewrite interface, that would relay back to the
filter.  I would like to know if there is a more efficient way to do
this, and if the above method is workable.

Thanks,
James


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Re: Virtual Alias Routing

Wietse Venema
James MacLachlan:
> Hi List,
>
> I have read the documentation, and do not understand if this is possible,
> but I think it should be.  I have a spam filter that is required to listen
> on the MX of my domain, but it does not support alias expansion, so the
> postfix server has to do the expansion then send the message back to the
> filter for final delivery.

That is a fairly standard: either one expands aliases before or
after a content filter.

> Is it possible to deliver virtual mailbox maps to the mda, but relay
> virtual alias maps back to the filter?

Postfix receives all mail from the filter, therefore expand your
virtual aliases in Postfix and be done with it. No need to filter
mail twice.

        Wietse
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Re: Virtual Alias Routing

James MacLachlan


On Wed, 28 Aug 2013, Wietse Venema wrote:

> James MacLachlan:
>> Hi List,
>>
>> I have read the documentation, and do not understand if this is possible,
>> but I think it should be.  I have a spam filter that is required to listen
>> on the MX of my domain, but it does not support alias expansion, so the
>> postfix server has to do the expansion then send the message back to the
>> filter for final delivery.
>
> That is a fairly standard: either one expands aliases before or
> after a content filter.
>
>> Is it possible to deliver virtual mailbox maps to the mda, but relay
>> virtual alias maps back to the filter?
>
> Postfix receives all mail from the filter, therefore expand your
> virtual aliases in Postfix and be done with it. No need to filter
> mail twice.
>
> Wietse
>

This solution requires delegating alias buckets to someone, rather than
everyone, which does not meet the enduser requirements.  The issue is a
conflict between the enduser requirments and the filter requirements, it
appears that I will not be able to satisfy one of them.

Thanks for the help.
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Re: Virtual Alias Routing

Wietse Venema
Wietse:
> Postfix receives all mail from the filter, therefore expand your
> virtual aliases in Postfix and be done with it. No need to filter
> mail twice.

James MacLachlan:
> This solution requires delegating alias buckets to someone, rather than
> everyone, which does not meet the enduser requirements.  The issue is a

If different users have different filter policies, then putting
Postfix before the filter solves that problem. When Postfix does
the alias expansion first, the filter knows who is receiving the
mail.

Looping mail from the filter through Postfix back again into the
filter is more than likely to cause mailer loops. Postfix routing
does not distinguish between an address that was received in RCPT
TO commands and an address that comes out of alias expansion.

        Wietse