OT: mailscanner integrated in transparent smtp proxy

Nick Brown nick at inticon.net.au
Tue Mar 30 12:53:26 IST 2010

On 30/03/2010, at 12:24 PM, Paulo Roncon wrote:

> Hi,
> this is OT but maybe someone can help me...
> I'm trying to come up with a transparent smtp proxy to filter  
> outbound mails in a ISP like environment with mailscanner.
> After a bit of googling i have smtp transparency, but not ip  
> transparency (SPF tests fail on the receiving end)
> has anyone worked in this problem?
> Tproxy? wccp? any ideias?

Putting aside the SPF standards, this seems like a horrible idea.

To the best of my knowledge (At the very least here in Australia + NZ)  
it is common place for ISP's to block SMTP via port 25, 587 and to a  
lesser extent now 26. As our bread and butter is in hosting, it is a  
nightmare having to keep track of a plethora of ISP's SMTP relays and  
walk customers through updating their email client - however I would  
much prefer it stay this way as opposed to wasting hours trying to  
troubleshoot mail issues when as far as the client is concerned it is  
being relayed via us - only to find the ISP is mangling SMTP.

Side note. Despite the annoyance - I think ISP's forcing customers to  
use an ISP supplied SMTP relay is a good thing.


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