Using DCC with forwarding?

Gary Mills mills@cc.UManitoba.CA
Tue May 21 14:21:16 UTC 2002

On Mon, May 20, 2002 at 09:15:20AM -0600, Vernon Schryver wrote:
> > From: Gary Mills <mills@cc.UManitoba.CA>
> How do you redirect mail?  When I try sending mail to another system
> via an alias, addr is resolved to the name.  Only when I really relay
> do I see addr not being resolved, and the mailer value = "esmtp".
> Perhaps you're using something fancy like virtual users.

Yes, virtual aliases.  I don't know if local aliases are resolved
by the time that milter is fed the mail.  There is also a sendmail
setting to defer lookups that may change things.

> > I've been giving this item more thought.  Sendmail resolves each
> > envelope recipient address into a triple: mailer:host:user.  (It does
> > the same with the envelope sender, but the result is unreliable.
> > That's why sendmail uses the SMTP peer address to control relaying).
> > In the case of local addresses, the mailer is `local', and the host
> > is empty.  For non-local addresses, the mailer is `esmtp', and both
> > the host and user fields are present.  Clearly, only local addresses
> > need per-recipient logs, because the mail server has no knowledge of
> > or control over users at other sites.
> It might be interesting to switch to the new versions of the dcc_conf
> file from homedir/dcc_conf (i.e. add DCCM_USERDIRS=userdirs) to see
> the "dir=" value.
> In other words, I think you can have per-recipient logs and whitelists
> for distant users, although the directory names will be odd.

Here's an example from my testing mail server:

  DATE: 05/19/02 11:08:11 CDT
  IP: localhost ::ffff:
  env_From: <mills@testing.UManitoba.CA>  mail_host=
  env_To: <>  dir=userdirs/esmtp/
  env_To: <>  dir=userdirs/esmtp/
  env_To: <nobody@testing.UManitoba.CA>  addr=nobody  dir=userdirs/local/nobody
  env_To: <>  dir=userdirs/esmtp/
  env_To: <>  dir=userdirs/esmtp/
  env_To: <daemon@testing.UManitoba.CA>  addr=daemon  dir=userdirs/local/daemon

So, yes, it does work.  It won't normally be useful because distant users
won't have access to the files, and you can't even tell which distant users
are valid and which aren't.

-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-

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