From: Wietse Venema (wietseporcupine.org)
Date: Mon Mar 01 2004 - 15:20:53 CST

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Mike Futerko:
> Hi Wietse,
>
> > > Here I mean Postfix checks SENDER address and then SENDER domain in the
> > > virtual_alias_maps, as shown in the logs attached. So why Postfix checks
> > > SENDER address/domain in recipient aliases? What is the reason to check SENDER
> > > address and domain in RECIPIENT aliases?
> >
> > Postfix recent snapshots check SENDER and RECIPIENT. This can stop
> > malware, and it is generally a bad idea to send mail with an invalid
> > return address.
>
> Yes, I understand and agree that it's bad to allow to send mail with
> invalid return address. However logs show that Postfix checks SENDER
> address in ALIAS tables,

If the sender address does not exist then Postfix rejects their mail.
To find out if the address does not exist, Postfix must examine the
tables with valid recipient addresses.

        Wietse

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