Dan Boresjo [dan(_at_)boresjo(_dot_)demon(_dot_)co(_dot_)uk] wrote:
Synopsis:
The %{u} macro expands to the username returned from an ident query
performed on the incoming connection.
Use cases:
1. Shared hosts - restricting outgoing SMTP to only the 'mail' user.
2. NAT Gateways - futher discriminating between hosts behind the
gateway.
I can see the benefit of this, but please be aware that:
a. ident responses do only make sense if the sending host is trustworthy and
not compromised, and
b. many mail server hosts don't run an ident service, and
c. SPF clients would have to support making ident queries.
I don't like (c) at all, and (a) and (b) probably reduce the usefulness of your
proposal to nearly zero.
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